












Drifts, Slopes, and Shafts 


By 

I.C.S. STAFF 


DRIFTS, SLOPES, AND SHAFTS 
Parts 1-2 


431 

Published by 

INTERNATIONAL TEXTBOOK COMPANY 

SCRANTON, PA. 


39 ^ 9/75 


Tlhn 

.If 


Drifts, Slopes, and Shafts, Part 1: Copyright, 1920, 1906, by International Text 
book Company. 

Drifts, Slopes, and Shafts, Part 2: Copyright, 1921, 1906, by International Text 
book Company. 


Copyright in Great Britain 


All rights reserved 


Printed in U. S. A. 










Grd 



j i t 



International Textbook Press 
Scranton, Pa. 







0 


CONTENTS 

Note. —This book is made up of separate parts, or sections, as indicated by 
their titles, and the pa*?e numbers of each usually begin with 1. In this list of 
5u nt u n , the tltles the parts are given ip the order in which they appear in 
the book, and under each title is a full synopsis of the subjects treated. 


DRIFTS, SLOPES, AND SHAFTS, PART 1 

Location of Mine Opening. 1- 8 

Definitions . 1 

Conditions That Determine Position of Opening. 2- 4 

Conditions That Determine Form of Opening. 5- 8 

Drifting . 9- 15 

Dimensions and Grade of Drift.-. 9- 10 

Methods of Drifting. 11- 15 

Beginning a drift; Narrow work; Location of shots; Cost 
of drifting; Blasting without preliminary cutting. 

Tunnels . 16- 26 

Tunneling in Loose or Running Ground. 16- 17 

Forepoling a tunnel; Wedging methods. 

Tunneling in Hard Rock. 18- 21 

Tunnel and Drift Portals. 22 

Tunnel Linings. 23- 26 

Slopes . 27^-28 

Dimensions; Construction; Shelter holes; Safety dog; 

Safety blocks; Derailing switch. 

Shafts . 29-48 

Principal Forms of Shafts... 29 

Factors That Determine Shaft Dimensions. 30- 36 

Disadvantages of small shafts; Usual shaft dimensions; 

Speed of hoisting; Table of well-known shafts; Output 
of hoisting plant; Width of shaft; Length of shaft. 

Sinking Tools and Appliances. 37- 41 

Buckets; Rope hooks and bridle chains; Guides for 
buckets ; Shaft coverings ; Dumping the bucket; Hoist¬ 
ing engine; Portable boiler. 

Head Frames and Other Shaft Structures. 42- 46 

Sinking head frame; Temporary head frame; Ventilation; 

Manway or pumpway. 

Methods of Lighting and Drainage. 47- 48 





















IV 


CONTENTS 


DRIFTS, SLOPES, AND SHAFTS, PART 2 

Pages 

Shafts, Continued . 49-120 

Shaft Sinking. 49- 75 

Preparatory Work. 49- 50 

Materials and appliances; Position of shaft; Shaft tem¬ 
plet or sill. 

Sinking Through Ground That Does Not Run.. . 51- 57 

First stage of excavation; Plumbing the shaft; Lining the 
shaft; Sinking through rock; Method of drilling, charg¬ 
ing, and firing holes; Shaft lining; Sinking in swelling 
ground. 

Sinking Through Quicksand or Running Ground. ... 58- 73 

Precautionary measures; Consolidating sand with ce¬ 
ment; Sand beds excluded by piling; Forepoling in 
quicksand; Shoes for shaft sinking; Lining suspended 
from surface frame; Triger, or pneumatic, method; 

Poetsch and Gobert freezing processes; Kind-Chaudron 
and Lippman systems. 

Shaft Timbering . 76-114 

Timbering in Various Kinds of Ground. 76- 84 

Effects of local conditions; Water pressure against lin¬ 
ing; Material of lining; Timbering in rock; Timbering 
in loose dry material; Timbering from bottom upwards; 
Timbering in swelling ground; Timbering in very wet 
ground or quicksand; Timbering a wet surface and 
subsoil. 

Provisions for Drainage of Water. 85— 88 

Water rings; Lodgements, or basins; Sump; Framing 
above sump; Coffer dam. 

Examples of Shaft Timbering. 89- 95 

Three-compartment shaft; Shaft sunk through quick¬ 
sand; Timber joints; Square-set timbering. 

Curbs . 96-97 

Timber, Masonry, and Metallic Linings. 98-107 

Masonry shaft lining; Metallic lining, or tubbing; Wood 
tubbing; Calculating thickness of metal and masonry 
linings; Metallic lining supported from surface; Steel 
shaft lining; Concrete lining with expanded metal. 

Special Shaft Work.108-114 

Retimbering a shaft; Enlarging shafts; Deepening shafts; 
Upraising. 

Contracts for Shaft Sinking.115-120 

Details otf contract; Specimen form of contract. 














DRIFTS, SLOPES, AND SHAFTS 

(PART 1) 

Serial 846A _ Edition 2 

LOCATION OF MINE OPENING 


PRELIMINARY CONSIDERATIONS 


INTRODUCTION 

1. Definitions of Terms.— Excavations for the purpose 
of developing coal seams are termed mine openings. They 
may be horizontal, inclined, or vertical, depending on the 
geological conditions, economy and efficiency in bringing the 
coal to the surface, and requirements of drainage and ventila¬ 
tion. 

If all or a considerable portion of a coal seam lies close to 
the surface, the overlying earth and shale, or rock, may be 
removed and the coal mined by the open quarry method. The 
removal of the overlying earth and shale is known as 

stripping. 

If the coal seam crops out on the surface, an opening driven 
horizontally into the seam is known as a drift. If driven 
horizontally through rock from the surface to a coal seam or 
underground from one coal seam to another, it is called a 

tunnel. 

If drifts and tunnels are at such a level in the seam, or if 
they cut the seam at such a level that all drainage from the 
workings above the elevation of their floors will flow to the 
surface by gravity, they are usually called water-level drifts 
and water-level tunnels, respectively. 


COPYRIGHTED BY INTERNATIONAL TEXTBOOK COMPANY. ALL RIGHTS RESERVED 





9 


DRIFTS, SLOPES, AND SHAFTS, PART 1 


If an opening is driven down the pitch in an inclined coal 
seam, it is known as a slope; if it is driven down grade 
through rock to a coal seam, it is known as a rock slope. 

If the opening is sunk vertically through overlying strata to 
a coal seam, it is called a shaft. 

2. The surface end of a drift or tunnel is known as its 
mouth. The upper, or surface, end of a slope or shaft is 
known as its head, top, or mouth, and the lower, or bottom, 
end is known as its foot, or bottom. 

Haulage roads, that are horizontal or nearly so, when turned 
off a slope are known as levels, or lifts. They are numbered 
successively from the mouth downward, as first level, second 
level, or first lift, second lift, etc. 


CONDITIONS THAT DETERMINE POSITION OF OPENING 

3. Position of Main Opening’. —The character and 
location of the main opening of a coal mine can be determined 
only after a careful study of the inclination and thickness of 
the coal seam and its overlying strata. In addition to this, it 
is necessary to take into consideration the extent and topog¬ 
raphy of the property; the best location for the tipple or 
breaker and the balance of the surface plant; also, the maxi¬ 
mum daily output desired, and the capital available for future 
development. 

While it is desirable that the main opening of a coal mine 
should be near the tipple or the breaker and at such a height 
relative to either one as to cause a minimum expense in outside 
haulage and handling, it is also possible that, ultimately, greater 
economy will be secured by having the opening at a consider¬ 
able distance from the tipple or breaker. 

If the capital available for development work is limited, it 
becomes necessary to have such an opening as will permit quick 
shipment of coal, from the profits of which more extensive 
development work may be done. Under such conditions the 
opening may be of such a nature as to allow its future use as a 
second opening, or at least as part of a second opening. 



DRIFTS, SLOPES, AND SHAFTS, PART 1 


3 


4. Position of Tipple or Breaker. —Whenever pos¬ 
sible, the position of the tipple or breaker and outside improve¬ 
ments should be dependent on the location of the main opening, 
rather than that the location of the opening should be depen¬ 
dent on the location of the tipple. 

W hether the coal is to be shipped to market by railroad, by 
water, or partly by either means, will have an important bear¬ 
ing on the location of the tipple or breaker. 

If the coal is to be shipped by rail, the tipple or breaker must 
be located at such a point that a connecting branch railroad or 
sidings may be constructed and operated at a reasonable cost 
per ton of output. Should the mine mouth be high up on a hill 
and the existing railroad be in the valley, it often pays to locate 
the tipple or breaker in the valley and to use a self-acting plane 
for running the coal to it. 

5. The main opening of a mine may be located several 
hundred yards away from the railroad and the surface forma¬ 
tion be such as to make the cost of a branch line and sidings to 
a point near the mine opening prohibitive. In this case a 
narrow-gauge railroad may be constructed over which to haul 
the mine cars from the mine to the tipple or breaker. How¬ 
ever, when the output will warrant the expense, it is preferable 
to locate the tipple or breaker near the mine opening and run a 
branch track to it from the main railroad. 

If shipments are to be made by water, or part by water and 
part by rail, the tipple or breaker must necessarily be located on 
the bank of the river or canal, at a point most convenient to the 
mine opening and where a branch track can be constructed to it. 

G. Connecting: Tipple or Breaker Witli Railroad. 

If the mine opening and the tipple or breaker must be located 
at a considerable distance from the main railroad, the branch 
connecting with the mine may be constructed wholly by the 
railroad company, partly by the railroad company and partly 
by the mine owners, or entirely by the latter. When con¬ 
structed jointly by the railroad company and the mine owners, 
the latter do the grading under the direction of the engineer- 


4 


DRIFTS, SLOPES, AND SHAFTS, PART 1 


ing officials of the railroad, and the railroad company furnishes 
the ties and rails and lays them. 

When the branch is constructed by the mine owners, a map 
showing its location, grades, curves, and the point where it is 
proposed to connect with the main line must be submitted to 
the railroad officials for their approval, because, as the haulage 
will be done by the railroad, they will require that the grades, 
curves, and point of connection with the main road shall be 
such as to make the operation of the branch line safe and as 
economical as possible. 

7. Extent of Mine. —The amount of territory that can 
be economically worked from one main opening will depend on 
the physical characteristics of the seam and the contour of its 
floor. A general idea of the contour of the floor of the seam 
will in most cases have been obtained from prospect holes and 
geological cross-sections. The opening should, preferably, be 
placed at the lowest part of the seam, so that the workings will 
drain by gravity and so that haulage grades favorable to the 
load may be secured. 

If the seam is flat and is opened by a shaft, it should be 
placed in the center of the field, if possible, so that the inside 
haulage costs will be at a minimum by reason of the shorter 
distances from the working faces to the shaft. 

With locomotive haulage it is practicable to have main haul¬ 
age roads extending a distance of 6,000 to 8,000 feet from the 
opening of the mine. Hence, if a shaft is sunk in the center of 
a flat seam it would be possible to work a tract of from 12,000 
to 16,000 feet square, or from 3,000 to 5,000 acres. But, con¬ 
ditions are generally such that it is advisable to restrict the 
acreage reached from one hoisting shaft to about 1,000 acres. 

8. Position of Second Opening.— In locating a sec¬ 
ond, or escape, opening, it is necessary to consider the use 
to which this opening is to be put and the requirements of the 
law regarding such openings. The law usually specifies a 
minimum distance between the main opening and the second 
opening inside of which it is not permissible to go. In general, 
it is desirable to make this distance as small as the law will 


DRIFTS, SLOPES, AND SHAFTS, PART 1 5 

allow, so as to quickly as possible provide a good circulation of 
air. 

At slope and shaft mines the second openings are generally 
utilized for lowering timber and supplies, and lowering and 
hoisting men. Often they are also utilized for conducting elec¬ 
tric wires, as well as steam pipe and compressed-air pipe 
into the mines, and for column pipe from the pumps; they are 
also used for main airways. While it is usually preferable to 
place the ventilating apparatus at the second opening, the posi¬ 
tion will, to some extent, also be governed by the system of 
ventilation and the kind of ventilator used. If the second open¬ 
ing is an upcast opening for the mine, the location of its mouth 
at a higher elevation than that of the main opening will assist 
the ventilation to some extent. 


CONDITIONS THAT DETERMINE FORM OF OPENING 

9. Effect of Local Conditions. —No definite rules can 
be given as to the most suitable form of mine opening. The 
choice of opening depends to a great extent on local conditions, 
of which the most important are the geological formation, the 
topography of the surface, and the distance between possible 
openings and the railway or waterway over which the coal 
must be shipped to market. 

When all the coal in a seam, or a considerable portion of it, 
can be mined by a drift or a tunnel from the surface, and such 
an opening is not too long, as compared with the tonnage of 
coal that can be won through it, then such an opening is pref¬ 
erable. It is assumed in this case that the mouth is within a 
reasonable distance of the tipple or breaker and that the topog¬ 
raphy is such that the expense of getting the coal to the tipple 
or breaker will not be excessive. 

10. Flat Seams. —If a coal seam is flat, or nearly so, and 
crops out on the property, a drift opening is best, provided it 
enters the seam at a point low enough to insure gravity drain¬ 
age; provided also that its mouth is so located that the coal 
can be transported to the tipple or breaker at a cost per ton 



6 


DRIFTS, SLOPES, AND SHAFTS, PART 1 


that will not exceed the sum of the costs per ton for hoisting, 
pumping, and transporting the coal from a shaft mouth to the 
tipple or breaker. In addition to this, it is necessary to con¬ 
sider the difference in the costs of the openings and their 
maintenance. 

A drift is the most inexpensive type of mine opening 
because its cost is wholly or partly covered by the value of the 
coal taken out. 

A tunnel costs considerably more per yard of length than a 
drift or a slope driven in the seam, but it usually requires little 
or no timber. 

11. When a coal seam that is flat, or nearly so, does not 
crop out on the property, and the overlying strata are too thick 
for profitable stripping, it must be opened by a shaft or a rock 
slope. Under such conditions the shaft or rock slope should 
be so located that the drainage will flow by gravity to the shaft 
or slope bottom and that the grades of the haulage roads will be 
in favor of the load. Also, its location should be such that 
the length of haul from the working faces on each side of the 
shaft or slope should be as nearly as possible of equal length. 

12. Inclined Seams With Outcrop.—In case a seam 
has a comparatively light inclination and crops out on the 
property, it may be so situated that the mouth of a slope can be 
located more conveniently to the tipple or to the breaker 
than can be the mouth of a shaft. A slope is then, generally, 
preferable to a shaft. 

But, if the seam has a comparatively heavy inclination and 
crops out on the property at a point where a slope can be 
located advantageously, a slope may be the best type of open¬ 
ing through which to mine the coal for several lifts. For 
mining the deeper coal a well-located shaft may be advisable. 

If an inclined seam dips with, or against, the slope of a hill, 
and a drift cannot be driven on its strike, it may be opened by 
a water-level tunnel driven at a right angle to the line of 
inclination of the rock strata, provided there is sufficient coal 
in the seam above the tunnel level to warrant the cost of the 
tunnel. 


DRIFTS, SLOPES, AND SHAFTS, PART 1 


7 


13. Sometimes an inclined coal seam is cut through by a 
ravine or a valley in such a way that the end of the seam is 
exposed, or can be exposed by removing a comparatively small 
amount of “wash,” or earth. In this case the best opening is a 
drift driven in the seam, provided the seam extends for a 
distance of 300 feet or more, measured on its pitch, above the 
level of the drift, and that it is practicable to convey the coal 
from the drift mouth to the tipple or breaker. Such a drift is 
said to be driven on the strike of the seam. 

1-1. Even when conditions are such that most of the coal 
in an inclined seam lies below water level, if 300 feet or more 
of the seam, measured on the pitch, lies above the level of a 
conveniently located drift or tunnel, that coal is usually mined 
through a drift or water-level tunnel, and the coal below water 
level is mined through a slope or a shaft. 

After the coal above water level has all been mined, the 
drift or water-level tunnel is frequently used as part of a 
second opening. Or it is utilized as part of a main airway or 
as an egress for water that is pumped to its level instead of 
being pumped to a higher elevation, as might be necessary if 
the drift or tunnel was not available. 

15. In an inclined seam, the coal below water level may be 
mined through a slope or a shaft. If the outcrop of the seam 
is high on a mountain, and the basin of the seam is very deep 
and under a valley, a shaft sunk in the valley may be much 
more economical than a long slope sunk from the outcrop, 
because the length of hoist will be much shorter, the height to 
which the drainage must be pumped will be less, and the cost 
of upkeep of the shaft will be less than that of a long slope. 
Besides, in many cases, the mouth of such a shaft will be 
located more conveniently to the tipple or the breaker. 

16. In the deep basins of the southern and middle anthra¬ 
cite fields of Pennsylvania, the coal above water level was 
opened by water-level drifts or tunnels. For several lifts 
below water level the coal was mined through slopes sunk from 
the outcrops of the seams. Finally, when the length of the 


8 


DRIFTS, SLOPES, AND SHAFTS, PART 1 


slope became such as to require a very long hoist and a high 
lift for the pumps, besides excessive costs for keeping the slope 
timbers in good order, shafts were sunk from points lower on 
the hills, or in the valleys, through which the coal below the 
lower levels of the slopes was won. 

17. Inclined Seams Without Outcrop. —For an 
inclined coal seam that does not crop out on the property, the 
best opening is a shaft, though in case the seam has an anti¬ 
cline at the determined location of the opening, it will be best 
to sink a rock slope from the surface on about the same pitch 
as that of the seam where the slope is to cut it. Which open¬ 
ing to choose will depend largely on whether the top of the 
shaft or the top of the rock slope will be in the best location to 
get the coal to a well-located tipple or breaker. 

18. Inclined Seams Worked From One Opening. 

When two or more inclined seams are worked from the same 
opening, they are generally connected by tunnels and the coal is 
brought to the surface through one opening. When the coal is 
above water level, the connecting tunnel or tunnels are usually 
extensions of the water-level tunnel from the first seam cut by 
it. When the tunnels are below water level, they are usually 
called cross-cuts or underground tunnels, the term cross-cuts 
being used when the connecting tunnel is only about 20 yards or 
less in length. 


DRIFTS, SLOPES, AND SHAFTS, PART 1 


9 


DRIFTS, TUNNELS, AND SLOPES 


DRIFTING 


DIMENSIONS AND GRADE OP DRIFT 

19. Introductory.— As the work of driving a drift, or 
drifting , is so closely related to entry driving, these subjects 
will be treated together. Drifts are used for prospecting pur¬ 
poses, for airways, haulage roads, traveling ways, and drainage 
purposes. In planning their size, shape, and timbering it is 
necessary to consider the purpose for which they are to be 
used. 


20. Dimensions of Drift. —The size of a drift depends 
on the output desired, the size of mining cars to be used, the 
character of the haulage, the thickness and character of the 
seam, and the character of the top and bottom rock. A weak 
rock often necessitates a narrow opening. The height of the 
drift should not exceed the thickness of the seam, unless abso¬ 
lutely necessary, as brushing (taking down) the roof or lifting 
(taking up) the bottom is always expensive dead work. The 
average height is from 5 to 7 feet, but when possible there 
should be 6 feet clearance above the top of the rail, so that a 
man can walk without stooping. The width varies from 6 to 
12 feet, for a single-track drift, to 12 to 18 feet for one that is 
double-tracked. A fair, average-sized single-track drift is 
6 feet wide at the top, 8 feet at the bottom, and 7 feet high in 
the center. Ample space should be allowed along the side for 
men to pass moving cars in safety and for a drainage ditch, 
air pipes, electric wires, etc. 

21. Number of Tracks. —The question of a single or 
double track should be decided before the work is started, but 




10 DRIFTS, SLOPES, AND SHAFTS, PART 1 


a single-track opening may be widened for a double track at 
any time in the later development of the mine, if a pillar of 
sufficient size is left along the passageway. Fixed rules can¬ 
not be given as to the size of a drift or as to when it should be 
built for single and when for double tracks, but the tendency 
is toward double tracks for short distances, and single tracks 
for long distances with partings or turnouts for the passing of 
cars going in and out of the mines. 

When double tracks are required two or three openings are 
frequently used instead of a single wide opening, particularly 
when the top and bottom of the seam are of such a character 
that a wide opening is impracticable. Separate single openings 
are safer and often cost less to maintain than wide openings, 
but wide passageways are generally more cheaply driven than 
two single passageways of the same combined area. The mate¬ 
rial left between two openings is called a pillar. The weight of 
strata resting on the pillars increases with the depth below the 
surface, hence the thickness of the pillars should increase as the 
depth of cover increases, or a sufficient thickness should be 
provided at the start to meet all future requirements. The 
thickness of the pillar between openings depends on the char¬ 
acter of the rock and coal, depth of cover, and the method of 
mining to be employed. 

22. Grade of Drift. —The grade of a drift should be 
sufficient for drainage, and be inclined toward the mouth of 
the opening, i. e., in favor of the loads. The theoretically per¬ 
fect grade is one on which the pull required to return the empty 
car to the face is exactly equal to that necessary to bring out 
the loaded car; but, as timber and supplies must be taken in, and 
since the track is not in uniformly good condition, this perfect 
grade is never attained. The grade should be at least 5 inches 
in 100 feet and should not exceed 1 or 2 per cent. With a 
grade under 1 per cent., the drainage is apt to be sluggish unless 
the side ditch is kept perfectly clean. 

A gutter, or ditch, is usually cut along one rib to carry off 
the water, and if the bottom is clay or other material that will 
wash away, a wooden trough is laid in it. If for any reason 


drifts, slopes, and shafts, PART 1 


11 


the grade of a drift or tunnel is such that drainage is not 
accomplished by gravity, a pump or a siphon is used, the drain¬ 
age pipe being usually laid on the floor at one side of the track 
or hung on the side timbers. 


METHODS OF DRIFTING 

23. Beginning* a Drift. — Before beginning the drift 
proper it is necessary to start an open cut in the side hill. The 
cut should be begun somewhat wider than the drift, the two 



Fig. 1 


side walls gradually converging toward the point where the 
drift goes under cover. As seen from Fig. 1, the cut should 
be continued until its height at the point where timbering 
begins is about 3 to 4 feet greater than the desired drift open¬ 
ing. At this point, if the roof rock has been exposed, or if the 
strata are sufficiently firm to be supported by timbering, a sub¬ 
stantial set of timbers is placed in position and drifting in coal 
is begun. If the material forming the roof is loose, the method 
of jorepoling, which is described later, is used until a firm roof 
is reached. 




12 DRIFTS, SLOPES, AND SHAFTS, PART 1 


Drifting may be carried on either by first undercutting and 
shearing the coal, as shown in Fig. 2, and then, if the coal does 
not fall by its own weight, wedging it or blasting it down; or by 
bringing down the coal entirely by blasting, as is the case in 
tunneling in rock. 

When the drift is from 6 to 12 feet wide, the work is called 
narrow work ; when it is wider than this, it is wide zvork. 

24. Narrow Work. —In driving narrow drifts, the miner 
shears the rib on one side, as in Fig. 2, and undercuts the coal 
to a depth approximately equal to the thickness of the seam, if 

the seam is not over 
5 to 6 feet thick. A 
shot is then placed 
near the unsheared 
rib. It is essential to 
avoid a tight shot , or 
a shot that is not 
given sufficient oppor¬ 
tunity to work, and a 
shot should not be 
placed too far on the 
solid. There is not 
the opportunity here, 
as in driving a room, 
to grip the shot, that 
is, to incline the hole at an acute angle to the face; but in 
narrow work the hole must be drilled more nearly parallel to 
the rib. The holes are generally shorter than in room work. 

The position and depth of the hole depend wholly on the 
shooting character of the coal. This varies in every seam, 
and the judgment and experience of the miner alone will 
dictate the best position and direction. Some seams may be 
worked by a single hole, but, in general, two holes are 
required to give the best results. In almost every seam, there 
is a softer and a harder stratum of coal. It is necessary to 
give the hole such a position and direction as to locate the 
charge so that its force will be expended more against the 




DRIFTS, SLOPES, AND SHAFTS, PART 1 13 


harder stratum. The hard coal may be at the roof of the seam, 
or it may lie next to the floor; or the hard coal may be central 
in the seam with a soft stratum above and below it. The coal 
may break freely at the roof, or it may have a tendency to hold 
fast to the roof. No rule can be given for these conditions 
except the general rule that the charge must always be located 
behind the greatest resistance. A charge located in a soft 
stratum will often cause the coal to seam out; that is, only the 
soft stratum will be blown out by the force of the blast, leaving 
the harder coal in place. When coal tends to seam out, the 
hole should always be inclined upwards or downwards across 
the strata, so that the charge is located in the harder stratum. 

25. Location of Shot in Narrow Work. —In Fig. 3 
(a) is shown the position and direction of the hole where a 



Fig. 3 


single shot is used for bringing down the coal in narrow work. 
The harder stratum lies next to the roof and the coal breaks 
freely at the roof. Such a hole in a 5-foot seam may be 
started 2 feet from the floor, 4 feet from the right rib, and 
inclined upwards and to the right at an angle of about 30°. 
The hole may be bored 4 feet deep, the shearing and under¬ 
cutting being 2 feet in depth; this will locate the charge but 
slightly on the solid or beyond the face of the shear. 

Fig. 3 ( b) shows the position and direction of the holes 
when two shots are used to bring down the coal, owing to 
the upper stratum being harder and not breaking freely from 
the roof. The holes are fired separately. 

It must be remembered, in locating a shot, that the weight 
of the coal is downwards, and with a good undercut and shear 
the weight assists in bringing down the coal shattered by the 

431—2 








14 DRIFTS, SLOPES, AND SHAFTS, PART 1 


force of the blast. In the cases illustrated in Fig. 3 (a) and 
( b ) the charge has been located in the upper stratum where 
the coal is harder. Fig. 3 (c) shows the position and direction 
of a hole when the lower stratum of coal is the harder. The 
undercut is in the underclay, and the coal breaks freely at the 
roof. It will be observed that the position of the shot is about 
central in the seam and inclines slightly downwards, having 
been started at a higher point in the face than in Fig. 3 (a) or 
( b ). This position of the charge will cause the fracture of the 
hard stratum of coal at the back of the undercut, and the soft 
stratum above will also be broken. 

When the coal is down, it is broken by sledges, if necessary, 
and loaded on the car. The rib on the opposite side from the 
shear is then trimmed as may be necessary. The operation is 
repeated by putting in another undercut and a new shear either 

on the same or the opposite 
side of the face. 


26. Wide Work.—In 
driving a wide drift, the 
coal is sheared close to one 
rib and undercut as before; 
but the shot, more or less 
inclined, is placed toward the center of the entry. The shearing 
and undercutting are usually made deeper than in narrow work. 
When the coal has been removed from one side of the drift, or 
entry, the same operation is repeated by undercutting the coal, 
the shot being placed near the center of the solid coal. The 
place is thus advanced in steps—first on one side and then on 
the other. 

When a drazv slate overlies the coal, it is usually allowed 
to remain up at the face. If necessary, one or two props are 
stood a short distance back from the face to protect the miners. 
The slate is either allowed to fall in the entry, say 20 or 
25 yards back from the face, or it may be wedged down later 
to secure greater headroom for the timbering and the cars. 
In order to avoid removing too large an amount of dirt from 
the mine, when there is a heavy draw slate, or to provide 



Fig. 4 




DRIFTS, SLOPES, AND SHAFTS, PART 1 15 


headroom in a thin seam, a wide drift, or entry, is driven and 
the draw slate, as it falls, is built along the rib as shown in 
Fig. 4. 

27. Cost of Drifting-. —The cost of drifting varies 
according to the width of the opening and the conditions of 
the seam. For narrow work, the miner is usually paid yard¬ 
age; i. e., a certain sum per linear yard of advance, the amount 
depending on the locality, the size of the drift or entry, and the 
character of the coal. He is sometimes also paid for the coal 
mined. In some localities, instead of yardage, the miner is 
paid an extra price per car or ton. In wide work, the miner is 
paid by the car or ton and is very seldom paid yardage. In 
ordinary coal, two men will drive an 8-foot entry from 4 to 
6 feet in a shift of 8 hours. 

28. Firing Time.— The specified time at which the 
firing of shots in the mine begins is known as the firing 
time. In entry driving or drifting, it is necessary to fire at 
shorter intervals than in room work; in many mines, firing is 
permitted in entries as soon as the holes are ready, although it 
may be prohibited in the rooms in the same mine except at 
firing time. 

29. Blasting Without Preliminary Cutting.— If 
the coal is neither undercut nor sheared, the method of driving 
differs from the methods already given only in the effect of 
the shot. Thus, if a short hole is driven at an acute angle with 
the face, it will, when fired, produce an opening at one side or 
in the center, known as a loose end. This loose end is of the 
nature of a shear or an undercut. When drifting in coal, care 
must be exercised in locating and charging the holes so that 
the coal will be broken as little as possible. 


16 DRIFTS, SLOPES, AND SHAFTS, PART 1 


TUNNELS 


TUNNELING IN LOOSE GROUND 

30. Preparatory Work.— The preceding description of 
the size, number of tracks, grade, drainage, etc. of a drift 
applies equally to a tunnel. When a tunnel is driven from the 
surface, an open cut is started, as in the case of a drift, but the 
subsequent work of driving, its rapidity, and the method of 
securing the sides and top, depend on the character of the 
strata through which the tunnel passes. 

31. Forepoling a Tunnel.— When tunneling in loose 
ground, the top, and sometimes the sides, of the tunnel must be 



supported by an arrangement of plank or lagging known as 
forepoling'. It consists in driving sharpened pieces of nar¬ 
row plank, or lagging, into the roof at a very slight pitch. The 
lagging rests on the collar of one timber set and is firmly held 
by having its end underneath the timber in the next set toward 
the entrance. 

In Fig. 5, a are the posts of the timber sets, b the caps, and e 
the top bridging. The front ends of the spiles g from any 
given set rest on the bridging e of the next advanced set, and 
the spiles for advancing the work are driven between the 
bridging and the cap, as shown. To force the spiles into the 
ground, so as to provide room for the placing of the next set, 

































DRIFTS, SLOPES, AND SHAFTS, PART 1 17 


tail-pieces i are placed behind the back end of the spiles as 
they are being driven. After the spiles have been driven for¬ 
wards the desired distance, another set is placed, the tail¬ 
pieces knocked out, and the front end of the spiles allowed to 
settle against the bridging of a new set. Where the face is 
composed of extremely bad material, it may be necessary to 
hold it in place with breast boards k held in place by props l 
that rest against the forward timber set. In a similar manner 
the side lagging h is placed in position. When breast boards 
are used, it is generally necessary to employ foot and collar 
braces between the sets, so as to transfer the pressure of the 
breast back through several sets. 

32. Forepoling a Drift. —The method of starting the 
forepoling at the mouth of a drift is shown in Fig. 1. Several 
sets of timbers are set up and long lagging driven over them 
into the earth beyond. By balancing the pressure of the earth 
on the points of the lagging with a weight of stone or timber 
on the outside end, they are held up and enough earth removed 
to allow another set being placed to support the lagging nearer 
the tunnel face. While practicable in rather loose ground, this 
method is not available in material containing boulders, and is 
dangerous when used in loose sand. 


TUNNELING IN RUNNING GROUND 

33. Available Methods. —The several methods em¬ 
ployed for excavating in running ground or loose sand are 
wedging, the use of metal shields, and the pneumatic process. 
As the latter two methods have been developed chiefly in con¬ 
nection with shaft sinking, they will be described in detail 
under that heading. 

34. Wedging Methods. —In some cases, it has been 
possible to drive through very fine, loose sand by simply 
wedging all or most of the material out of the way by means 
of wedges. An example of this kind is shown in Fig. 6, in 
which a are the posts of regular timber sets; b, the side plank¬ 
ing ; c, the spiling driven, as in forepoling, to support the top; 



18 DRIFTS, SLOPES, AND SHAFTS, PART 1 


d, the wedges; e, the tailing pieces; f, the floor; g, the bridging 
pieces; and h, the cap pieces. The timber set below e is only 
a temporary one, and is removed after the spile c is driven 
forwards. 

The wedges d are driven into the face oy means of a ram 
made of a piece of timber swung from the roof. They simply 



Fig. 6 


crowd the material away from in front of the excavation; if 
the pressure becomes so great that they cannot be driven any 
farther, a few auger holes are bored into the face to relieve the 
pressure by allowing some of the material to flow into the drift. 
Wedges are driven into the floor with a mallet as fast as those 
in the face advance, and are ultimately covered with a plank 
floor /. 


TUNNELING IN HARD ROCIv 

35. Drilling’ and Blasting.— If rock crops out at the 
point selected for the location of a tunnel, a face must be 
cleared away by drilling and blasting. The work differs from 
that previously described, in that no undercutting and shearing 
is done. The rock is removed entirely by blasting, for which 
























DRIFTS, SLOPES, AND SHAFTS, PART 1 


19 


purpose one or more series of holes are drilled more or less 
inclined to the face. These holes should be so arranged as to 
permit the drills to be easily handled and to give the smallest 
possible number of holes and require a minimum weight of 
explosives. 

36. If a solid face of rock is exposed, it is necessary first 
to make a wedge-shaped opening, known as a key hole, in 
the face. This key hole is produced by drilling the holes at 
such an angle to the face that the hole produced by the blast¬ 



ing will be shaped as a wedge, known as a key cut, with its 
pointed end innermost. The succeeding shots will then do 
deeper and more effective work. 

37. The common method by which to produce a key hole is 
known as the square cut, or American, method, which is illus¬ 
trated in Fig. 7 in several views. Thus, a front elevation of 
the face is shown at (a); a sectional elevation at (h) ; a sec¬ 
tional plan at (c) ; and at ( d ) a sectional elevation taken at the 














20 DRIFTS, SLOPES, AND SHAFTS, PART 1 


near wall of the tunnel. In all views the drill holes are indi¬ 
cated by dotted lines and the outer openings by blackened 
circles. The arrangement of the holes corresponds with that 
used in driving an ordinary 7 ft.X7 ft. mine tunnel. 

The rows of drill holes, shown in a and b, view (a), 
are placed symmetrically on either side of an imaginary, ver¬ 
tical center line of the face and at a distance of from 2 \ to 
3J feet, center to center. The angle of inclination to the face 
is shown in the various views. Other rows c and d are placed 
near the rib as shown. These rows and the top and bottom 
holes of the center rows are placed as near as possible to the 

rib, to the roof, and to the 
floor, respectively. It is to 
be noted that the more nearly 
parallel the holes are to the 
general direction of the tun¬ 
nel, the straighter will the 
cut be made. 

38. As the number and 
inclination of the holes de¬ 
pend on the character of the 
rock, no definite rules can be 
given that will apply to all 
cases; experience must be 
the general guide. Under 
ordinary conditions it is found that 14 to 16 holes are ample 
for the face of a 7 ft.X7 ft. tunnel. In the first volley the 
holes i to 8 are fired, and in the second volley the side holes p 
to 16 . In large tunnels these holes are sometimes as long as 
10 feet and bring out from hard rock a cut of from 2 to 
3 yards in length. 

39. The drill holes may be arranged so that the key cut is 
produced either in the center, at the side, or at the bottom of 
the face, depending on the structure of the rock. If the rock 
texture is uniform and there are no joints, or slips, the holes 
are placed symmetrically with respect to the face center line, as 
in Fig. 7. They may also deviate from the American method 










drifts, slopes, and SHAFTS, PART 1 21 

by being arranged in circles about the key cut instead of in 
rows parallel to the ribs. 

When a slip, or joint, occurs in the rock as at a b, Fig. 8 , 
advantage may be taken of it by locating the holes for the first 
volley near the joint, and by inclining them toward the plane 
of fracture. Only the holes that are needed for cutting the 
opposite rib, such as p, io, and n, are inclining in the opposite 
direction. The order of firing is as follows: First, / and 
fired together; second, J, 4 , and 5 , fired consecutively; third, 
6 , 7 , and 8, fired consecutively; and, fourth, p, 10 , and 11 , 
fired consecutively. 

40. It should be remembered that a rock that is hard to 
drill is not necessarily difficult to blast, and vice versa. Thus, 
a granite or some form of metamorphic rock, such as a very 



hard sandstone that is jointed or brittle, may be difficult to 
drill, but will break easily with the use of comparatively few 
holes and a small amount of powder. A clay shale, however, 
which is soft and tough and easily drilled, may not yield as 
readily to the blast. 

41. Removal of Material. —At first, the material pro¬ 
duced by blasting is removed by shoveling it to the mouth of 
the tunnel. As the work proceeds, wheelbarrows are used; 
and, finally, wooden or iron rails are laid on which a small car 
is run, similar to that shown in Fig. 9. Unless the material 
excavated from the tunnel is coal or ore of some value it is 
simply dumped at its mouth and spread to form a nearly level 
surface with a slight grade away from the mouth and toward 
the dump. This will furnish track room and a convenient site 
















22 DRIFTS, SLOPES, AND SHAFTS, PART 1 


for the necessary surface buildings. The cars are at first 
pushed out by hand, but as the face of the tunnel advances, a 
mule or a horse is used for pulling them. 


TUNNEL AND DRIFT PORTALS 

42. Various Forms of Portals.— A tunnel or drift 
mouth, or portal, is frequently constructed as in Fig. 10 (a) 



Fig. 10 


and (b), the mouth being surrounded by a frame of sawed 
timber and rough walls. Some of the more recently built 
portals have masonry arches built over the mouth of the 





































DRIFTS, SLOPES, AND SHAFTS, PART 1 23 


tunnei or drift, as in Fig. 10 (c), ( d ), and ( e ). Or, the 
portal may be constructed of concrete, as shown at (/). The 
stonework or concrete construction at the portal is carried out¬ 
wards in the form of side wing walls; it is also frequently con¬ 
tinued underground to a point where a solid formation is 
encountered. 


TUNNEL LININGS 

43. Reasons for Lining; a Tunnel.— Usually, a tunnel 
does not require lining and sometimes no timber at all is 
required after a solid rock face is encountered. Under some 
conditions, however, either a portion or the entire length of the 
tunnel must be timbered or lined with brick or stone or con¬ 
crete. When the roof of the tunnel must be supported, it is 
customary to employ timber or steel supports, the same as in a 
drift, though brick, stone, or concrete lining may also be used. 

In case the bottom or the sides of the tunnel are soft, and 
the weight of the overlying rock tends to cause the floor to 
rise and the sides to bulge, it is necessary to line the tunnel. 

44. Various Forms of Lining;.— Various forms of 
lined tunnels of rather large sectional area are shown in 
Fig. 11. The systems of lining shown will apply to tunnels of 
any sectional area. For a hard bottom, the form of arch 
shown in Fig. 11 (a) is often used. It consists of a full semi¬ 
circular arch that has its spring lying a few feet above the floor 
of the tunnel. The side walls may or may not be carried below 
the floor of the tunnel, according to the character of the floor. 
The spring; of an arch is the point where the vertical side 
of the arch joins the curved portion. 

For a soft bottom, the form of lining shown in Fig. 11 ( b ) 
is used. The lower portion a, which is an inverted flat arch, is 
laid first; it is kept in advance of the side walls and the arch 
forming the roof of the tunnel for the purpose of allowing the 
work a short time for setting before the weight of the arch is 
placed on it. In constructing the arch forming the roof of the 
tunnel, it is supported at intervals by centers, or wooden frames, 
cut to the required outline of the arch. These centers are 



24 DRIFTS, SLOPES, AND SHAFTS, PART 1 


placed from 2 to 3 feet apart, and are covered above with 
short lengths of lagging on which the arch rests while being' 
built. As each section of masonry is completed, the space 
behind the masonry is firmly packed with sand, ashes, cinders, 
slack, or other fine material in order to distribute the roof 
pressure evenly on the arch. A short time is given for the 



Fig. 11 ( d > 


work to set, when the centers are taken down and moved for¬ 
wards to another section. Sometimes iron centers are used 
instead of wooden ones. 

45. Where the side pressures are heavy, one of the forms 
of arch shown in Fig. 11 (c) and ( d ) is employed. In that 
shown at (c), the side walls are made to conform with the 






































DRIFTS, SLOPES, AND SHAFTS, PART 1 25 


segments of a circle or of an ellipse. Should the tunnel be sub¬ 
jected to a very heavy pressure all around, due to the soft 
nature of the ground, the section of the tunnel may be entirely 
elliptic, as shown at ( d ). 

In the building of tunnel walls, very little mortar should be 
used between the joints, and no old wood or material liable to 
decay should be left in or behind the wall. 

46. Material of Lining’.— The material used in con¬ 
structing tunnel linings is generally stone, brick, or concrete . 
Concrete possesses the advantage of affording an even dis¬ 
tribution of pressure, of being very rapidly constructed, and 
much less costly than masonry. 

Concrete is composed of cement, sand, and crushed stone 
(or some substitute) mixed in such proportions as to be suit¬ 
able for the purpose for which the concrete is to be used. 
Gravel, furnace slag, cinders, brickbats, broken slate, etc. are 
often substituted for the broken stone, because they are 
cheaper and often more readily obtained, but they do not give 
so good a concrete. 

47. The cement generally used in making concrete that is 
subjected to heavy pressure, is that known as Portland, 
cement. This cement is made by mixing certain kinds of 
crushed limestone and clay or other materials rich in silica, 
alumina, and lime, then burning the mixture to a clinker and 
grinding this clinker until it is reduced to a nearly impalpable 
powder. From the nature of this process, involving the arti¬ 
ficial mixture of the different ingredients, the resulting product 
is sometimes called artificial cement, but is more generally 
known as Portland cement. 

When cement is mixed with water to a stiff paste and 
allowed to stand a sufficient time, the paste undergoes chem¬ 
ical change and a solid mass results. This setting, as it is 
called, usually requires but a few hours at most. After the 
setting, a slower chemical action sets in, and the mass grad¬ 
ually gains in strength. Usually this gain of strength, or 
hardening, extends over a period of from 6 months to a year— 
sometimes even beyond this period. Chemists who have 


26 DRIFTS, SLOPES, AND SHAFTS, PART 1 


examined the chemical composition of cement do not agree as 
to the changes that it undergoes when it sets. 

48. In mixing concrete, the best proportions of the ingre¬ 

dients will depend on their character and the purpose for which 
the concrete is to be used. For engine foundations, mine open¬ 
ings, tunnel and shaft linings, the following proportions will 
produce a satisfactory mixture: 1 part, by measure, of Port¬ 

land cement; 3 parts sand; 6 parts broken stone. 

The sand should be clean, sharp, gritty, and free from dirt 
or other foreign matter; when it contains any considerable 
amount of mud or dirt, it should be washed. The broken 
stone or slag should be of suitable sizes, preferably such as 
will pass through a ring with a 2-inch opening. Modern engi¬ 
neering practice does not object to the presence of the finer 
particles of stone in the mass. It will, consequently, not be 
necessary to screen the stone before using. 

49. It is important that the concrete be thoroughly mixed, 
to insure that all the spaces between the broken stones are filled 
by the cement and sand. Mixing may be done by machine or 
by hand. Machine mixing is the better and gives more uniform 
results; it is also more economical where large quantities of 
concrete are to be used. Hand mixing may be resorted to 
where the quantities of concrete required are not sufficiently 
large to warrant the use of machinery. 

In mixing concrete by hand, the sand and cement should 
first be mixed dry on a platform. Water is then added and 
the mixture is worked into a mortar. The use of too much 
water should be avoided; just enough to form a stiff paste is 
sufficient. The stone is first wetted and then added to the 
mortar, and the whole mass is thoroughly incorporated by 
turning over several times with shovels, until each stone is 
coated with mortar and the stones are evenly distributed 
through the mass. Concrete, after being mixed, should be 
placed in position immediately and not allowed to stand long 
enough to get an initial set before placing. After being placed 
in position, it should be well tamped with wooden or iron 
rammers. The tamping should be just sufficient to bring the 


DRIFTS, SLOPES, AND SHAFTS, PART 1 27 


water to the surface. Excessive tamping will disturb the 
intimate mixture of the ingredients that is so desirable. 


SLOPES 


SLOPE TIMBERING AND SAFETY APPLIANCES 

50. Dimensions of Slopes. —A slope may be classified 
as an inclined drift or tunnel dipping into a coal seam or other 
strata at any inclination between horizontal and vertical. 
Slopes vary in width and in height. The width depends on 
whether they are to be single- or double-track slopes and 
whether extra space is to be allowed on one side for electric 
wires and for steam, compressed-air, or column pipes. The 
height depends on the thickness of the coal seam or on the 
height of the cars to be used on the slope. Whether a slope 
should be single or double tracked depends on the extent of 
the body of coal to be worked and on the daily production. 

51. Construction of Slope. —The material excavated in 
sinking a slope is generally removed by means of a temporary 
hoisting engine, and the drainage is effected by pumps placed 
on trucks that can be lowered as the work progresses. 

The timbering of slopes of very light pitch corresponds with 
that employed in a drift or in a tunnel having the same char¬ 
acter of roof and floor. As the pitch of a slope increases, the 
timbers are underset , or made to lean slightly up the pitch. 
The amount of undersetting varies with the inclination of the 
slope. 

On steep slopes, the feet of the props, or legs, usually rest 
on heavy squared or hewn timbers, known as mud-sills, 
extending across the floor of the slope at right angles to its 
center line. These mud-sills are set into the ribs of the slope, 
and the props, or legs, are mortised into them. On very steep, 
wide slopes, the mud-sills often have posts, known as buntons, 
between them; and in addition, the rails of the track are laid 
on squared timbers that run longitudinally with the rails, these 
timbers being spiked or bolted to the mud-sills. 




28 DRIFTS, SLOPES, AND SHAFTS, PART 1 


SAFETY APPLIANCES 

52. Shelter Holes. —When slopes are of light pitch and 
are used by the men as traveling ways, refuge, or shelter, 
holes should be provided; in particular, if men are frequently 
employed on them in making repairs. In some states, they are 
required by law, owing to the liability to accident to men by 
being caught and squeezed between the rib and a trip of cars, 
or by the breaking of the hoisting rope or car couplings, or by 
the possibility of cars descending the incline before being 
attached to the rope. 

53. Safety Dog. —Hoisting and lowering of cars, while 
men are employed on the slope, is not permitted in most states. 
On slopes of light pitch, a heavy trailing iron bar, known as a 
safety dog, is often attached or coupled to the drawbar at 
the rear of the ascending car or trip of cars. The lower end of 
this dog, which may be either pointed or split, is allowed to 
drag along the track as the car proceeds up the slope. If the 
hoisting rope or a coupling breaks, the weight of the car on 
the incline forces the dog into a sill or into the floor, and the 
cars are either stopped or derailed. 

54. Safety Blocks. —Devices known as safety Mocks 
are necessary at the knuckle or at the head of all inclines, and 
in some states are required by law. They consist of blocks so 
arranged as to prevent cars descending the incline before all is 
ready and the signal given. These blocks are shaped and 
arranged so that ascending cars will pass them without diffi¬ 
culty, but they automatically return to place when the car has 
passed. They will, however, stop a car moving toward the 
knuckle, unless the blocks are moved aside by the topman, or 
by the engineer in the engine room. 

55. Derailing Switch.— A derailing switch is some¬ 
times employed either in place of or in conjunction with 
safety blocks. This is an automatic spring switch that permits 
an ascending car to pass on the main track but will derail a 
car passing to the slope unless the switch is properly set by the 
topman or from the engine room. 


DRIFTS, SLOPES, AND SHAFTS, PART 1 29 


SHAFTS 


FORMS AND DIMENSIONS OF SHAFTS 


PRINCIPAL FORMS OF SHAFTS 

56. European and American Forms. —A shaft may 
be either circular, elliptic, polygonal, or rectangular in cross- 
section. The first three forms are better adapted to withstand 
pressure than the rectangular, but they are more difficult to 
timber, and there is always a considerable area of the cross- 
section that is not available for hoisting. Such shafts are usu¬ 
ally lined with brick, masonry, concrete, or metal instead of 
timber and are common in many European countries, while 
rectangular shafts are generally used in the United States. 
The practice of lining shafts with concrete is growing in the 
United States and many of these have their sides and ends 
made as arcs of circles, so as to present an arch to the side and 
end pressures. The approximate section of the shaft is then 
elliptical. Rectangular shafts are either oblong or square, the 
former being the usual form for a hoisting shaft, while the 
latter is often used for a small prospect shaft, or for a second 
opening to be used as an escape shaft or an air-shaft. Rec¬ 
tangular shafts are not usually lined with masonry on account 
of the danger of the walls bulging, owing to the pressure of the 
strata behind them, although a number of rectangular shafts 
have been lined with concrete; timber of sufficient size is gen¬ 
erally used for the lining in these shafts, and when bulging 
takes place, any of these timbers can be taken out and replaced 
by others after the trouble has been removed. 

57. Shaft Compartments. —A shaft is usually divided 
into two or more compartments, either by buntons or cross¬ 
timbers placed one above another and spaced from 6 to 8 feet 
apart, or by solid partitions formed of 3-inch or 4-inch plank- 


431—3 




30 DRIFTS, SLOPES, AND SHAFTS, PART 1 


ing. If there are but two compartments, both of them may be 
hoistways or one may be a hoistway and the other a pumpway 
and ladderway. If there are three compartments, two of them 
are hoistways, and the third, and smaller, compartment, which 
is at the end of the shaft, is used for a manway and pumpway 
and for carrying steam or compressed-air pipes or electric 
wires into the mine. 


FACTORS THAT DETERMINE SHAFT DIMENSIONS 

58. Disadvantages of Small Shafts. —The size of a 
shaft depends on the use for which it is intended, and is 
determined by the hoisting, drainage, and ventilating condi¬ 
tions at the given mine. Before commencing to sink, a careful 
estimate should be made as to the size required for all future 
developments of the mine. Nothing is saved in sinking a shaft 
of too small dimensions, for the work of excavation is more 
easily accomplished in a large shaft, while the serious annoy¬ 
ance and limitations of a small shaft, and the great expense of 
enlarging a shaft already sunk, warrant a shaft of generous 
size. A tight shaft is one in which there is but little space 
between the curbing and the edge of the cage. In such a shaft, 
the cage acts like the piston of an air pump, moving the doors 
in the mine, and causing a general disarrangement of ventila¬ 
tion. In such a shaft, also, a very small amount of ice will 
interfere with hoisting. 

59. Usual Shaft Dimensions. —Shafts for coal mines 
vary in size from 5 ft.XlO ft. to 12 ft.X54 ft. inside the 
timbers. Interesting data about some leading American coal 
shafts are shown in Table I. 

60. Speed of Hoisting.— The size of a hoisting shaft is 
determined by the output of material required, the depth of 
the shaft, the speed of hoisting, the size of the mine car, and 
the number of cars hoisted at one time. The speed of hoisting 
is commonly understood to mean the maximum speed at 
which the cage moves during the hoist. This speed and the 
time lost in starting and stopping vary with the depth of the 
shaft. In general, the deeper the shaft the greater is the speed 



TABLE I 

TABLE OF WELL-KNOWN SHAFTS 


31 



I L T 87B 


16 


Depth completed, 1,150 feet. 






































32 DRIFTS, SLOPES, AND SHAFTS, PART 1 


of hoisting allowed, and the greater the speed the greater is the 
proportional loss due to starting and stopping the engine. This 
loss of time in starting and stopping varies from 3 to 10 sec¬ 
onds. The time consumed, between hoists, in caging and 
uncaging cars varies according to the style of equipment and 
the manner of caging cars employed. For ordinary conditions, 
it can safely be assumed to be from 5 to 15 seconds; and this 
amount added to the allowance made for the loss of time in 
starting and stopping the engine, or from 3 to 10 seconds, 

makes a total allowance be¬ 
tween hoists of from 8 to 


TABLE II 


Depth of Shaft 

Speed of Hoisting 
Feet per Second 

100 

10 to 15 

200 

15 to 20 

300 

20 to 25 

400 

20 to 35 

500 

25 to 40 

600 

30 to 50 

800 

30 to 50 

1,000 

30 to 50 


The speeds of hoisting for 
shafts of different depths are 
given in Table II. 

61. Output of Hoist¬ 
ing* Plant.— In estimating 
the output of a hoisting plant 
it is necessary to make a cer¬ 
tain allowance for delays, 
varying from 5 to 10 per 
cent., according to the char¬ 
acter of the hoisting plant. Thus, if hoisting is performed 
in 10 hours and if a delay of 5 per cent, is allowed, the 
net time of hoisting will be 95 per cent, of 10 hours, or 
.95 (10X60) =570 minutes. The total daily output divided 
by the net time of hoisting, in minutes, gives the required output 
per minute. The depth of the shaft, in feet, divided by the 
speed of hoisting, in feet per second, gives the time per hoist, 
in seconds, approximately, though it does not take account of 
the time lost in accelerating the engine in starting. The time 
per hoist plus the time for caging and uncaging gives the total 
time for each trip of the cage, in seconds. Then, 60 seconds 
divided by the time per trip gives the number of trips per 
minute. The output per minute divided by the trips per 
minute gives the weight of material hoisted at each trip of the 
cage. If one car is hoisted at a time, this will give the capacity 








DRIFTS, SLOPES, AND SHAFTS, PART 1 33 


of the car; if two cars are hoisted at a time, the capacity of the 
car is obtained by dividing the weight hoisted by two, etc. 
The capacity of a car, in cubic feet, is found by dividing the 
weight of material, in pounds, carried by the car by the weight 
of a cubic foot of the material hoisted. A cubic foot of any 
solid material equals the weight of a cubic foot of water 
(62.5 pounds) multiplied by the specific gravity of the material. 
Table III shows the weight, per cubic foot, of anthracite and 
bituminous coals of different specific gravities solid and broken, 
the latter being given for both loose and moderately shaken 


TABLE III 


Kind 

Specific 

Gravity 

Weight, Pounds per Cubic Foot 

Solid 

Broken 

Loose 

Moderately Shaken 


1.4 

87.50 

49 to 54 

53 to 58 


1.5 

93.75 

52 to 58 

56 to 62 

Anthracite 

' 1.6 

100.00 

55 to 61 

60 to 67 


1.7 

106.25 

59 to 66 

64 to 70 


' 1.2 

75.00 

41 to 46 

45 to 50 


1.3 

81.25 

45 to 50 

49 to 54 

Bituminous 

1.4 

87.50 

49 to 54 

53 to 58 


1.5 

93.75 

52 to 58 

56 to 62 


coal. Coal, when broken, occupies about 1.5 the space occupied 
by the same amount when solid; the weight of the broken coal 
is, therefore, about two-thirds that of the solid coal. 


62. Width of Shaft. —The size of the car to be hoisted 
determines the width of the shaft. The length of the box of a 
mine car is determined by the formula 



in which /= inside length, in feet; 

c = capacity, in cubic feet ; 

b = average breadth, in feet; 

d = depth, in feet, including the topping. 


















34 DRIFTS, SLOPES, AND SHAFTS, PART 1 


To the inside length of the car calculated by this formula, 
must be added the thickness of the end planks, each end being 
from 1 to 2 inches thick, and the length of the bumpers at each 
end of the car, from 4 to 10 inches, according to the style of 
car used, in order to obtain the length of car, out to out of 
bumpers. To this must be added 6 to 8 inches for clearance 
between each end of the car and the cage, and 6 to 9 inches 
more for clearance between each end of the cage and the shaft 
timbers, to obtain the width of the shaft in the clear. 

Cars, for use in coal mines, vary from 4 to 6 feet in width, 
from 5 to 10 feet in length, and from 2 to 5 feet in height. 
Their capacities vary from 1,000 to 8,000 pounds of coal and 
their weight from 500 to 4,000 pounds. 


Example. —Find the width of a shaft required for hoisting an out¬ 
put of 1,200 tons of bituminous coal per day of 8 hours, from a depth 
of 500 feet; the seam is 5 feet 6 inches thick, and has a good roof and 
floor; the specific gravity of the coal is 1.3. 


Solution. —Allowing 5 per cent, for delays, the net time of hoisting is 


.95 (8X60) =456 min.; and the output is 


1,200X2,000 

456 


=5,264 lb. per min., 


nearly. 

Referring to Table II, it is found that the speed of hoisting in a 
shaft 500 ft. deep varies from 25 to 40 ft. per sec. Assuming 25 ft. per 
sec., the time of hoisting one trip is- 2 ™=20 sec. Assuming 10 sec. for 
the time of caging and uncaging, the total time for each hoist is 20+10 
60 sec. 

=30 sec. Then ^(j— = 2 hoists per min., and if one car is hoisted at a 
time, the weight of material per hoist is -Mr 4 - =2,632 lb. of coal. 

In Table III, the weight of bituminous coal having a specific gravity 
of 1.3 is given as varying from 45 to 50 lb. per cu. ft., when broken 
(loose). For the ordinary mine run, assume 48 lb. per cu. ft.; then 
the capacity of a car is J if 1 =about 55 cu. ft. 

Assuming that the depth of coal on the car, including topping, is 
30 in. (24 ft.) and the inside width 40 in. (34 ft.), then the inside 
length is 


55 




55 55X6 


= 6.6 ft. =6 ft. 8 in. 


bd 34X2+ YXf 50 
Adding, to the inside length, 4 in. for the ends of the car and 12 in. 
for bumpers, the total length of car will be 8 ft. Then adding 3 in. 
clearance, between each end of the car and the cage, and 9 in. at each 
end for shaft clearance, the required width of the shaft is 10 ft. in the 
clear. Ans. 






DRIFTS, SLOPES, AND SHAFTS, PART 1 35 


63. Length, of Shaft. —Ordinarily, the length of the 
shaft must be such as to provide for two hoistways, and a 
pumpway or manway. The width of each hoisting compart¬ 
ment should be such as to give at least 6 inches of clearance 
between the greatest width of the car, out to out, and the 
guides. Allowance must be made also for the width of bun- 
tons separating the two hoistways, the thickness of the guides, 
and the width of buntons separating the hoisting compartment 
from the pumpway. According to the size and depth of the 
shaft and the character of the strata, the thickness of the 



buntons will vary from 4 to 12 inches. The size of the guides 
often employed in hoisting shafts is 4 in.X4 in., and the guides 
are commonly bolted or spiked to the buntons, the heads of 
the bolts or spikes being countersunk in the guides. 

In Fig. 12, the width of the car is shown as 40 inches, out 
to out, while the clear width between the guides in each hoist¬ 
way is 4 feet 10 inches, giving a clearance of 9 inches on each 
side of the car. The size of the guides is 4 in.X4 in., making 
the total width of each hoistway 5 feet 6 inches. The buntons 
shown in the figure are 6 inches wide and the pumpway 5 feet 























36 DRIFTS, SLOPES, AND SHAFTS, PART 1 

wide, making the total length of the shaft, in the clear, 17 feet. 
The width of the hoistway also depends on the number and 
size of cars hoisted at one time, and whether two cars are 
placed side by side on the cage, cr one above the other on a 
double-deck cage. 

G4. Fig. 13 shows a sectional elevation of a shaft where 
two cars are hoisted side by side on the cage. The entire 
length of the shaft in the clear, including hoistways and pump- 
ways, is 28 feet, giving two hoistways each 9 feet 10 inches in 



Fig. 13 


the clear, between guides, and a pumpway 5 feet in the clear. 
The guides are each 4 inches and the buntons 6 inches wide; 
the width of the cars is 46 inches, giving a clearance of 
8 inches on each side, and 10 inches between the cars. This 
is a very large shaft, being capable of accommodating an output 
of between 3,000 and 4,000 tons per day. 































DRIFTS, SLOPES, AND SHAFTS, PART 1 3 / 


SINKING TOOLS AND APPLIANCES 


HOISTING EXCAVATED MATERIAL 

65. Buckets.—A large number of tools and appliances 
are required in sinking, but the most of them are used only in 
special cases, where the conditions of the strata make them 
necessary. 

The buckets used for hoisting the material excavated in sink¬ 
ing are usually made of boiler iron or steel; two of the many 
shapes are shown in Figs. 14 and 15. 

The bucket shown in Fig. 14 is sup¬ 
ported from chains attached by a 
spring hook to ears on its sides and is 
dumped by being tilted by means of 
the handle shown. These buckets are 
from 2\ to 3 feet in height, about 27 
inches in diameter at the top, 18 inches 
in diameter at the bottom, and hold 
about 6 cubic feet. They weigh about 
150 pounds. 

66 . The form of bucket shown in 
Fig. 15 varies from 16 to 28 inches 
in diameter at the top, from 14 to 28 
inches in diameter at the bottom, and 
from 26 to 38 inches in height; it varies 
in weight from 180 to 470 pounds and in capacity from 2\ to 
14 cubic feet. The bail a is attached at a point below the center 
of gravity of the bucket so that the bucket has a tendency to 
turn over and empty itself. To prevent this while hoisting, a 
short pin b is riveted to the side and an ordinary chain link 
sliding on the bail is slipped over it. While these buckets are 
easily dumped, numerous accidents have been caused by their 
overturning in the shaft while hoisting men or material. 

A bucket is often made by sawing an oil barrel just above 
the second hoop from the top, and riveting to the lower part 














38 DRIFTS, SLOPES, AND SHAFTS, PART 1 


substantial eyes for securing the bail to the bucket. Boxes 
with drop bottoms are sometimes used instead of buckets for 
hoisting, and those using them claim a 
greater speed in the removal of material 
than with buckets; they are, however, dan¬ 
gerous, on account of premature opening of 
the bottom during hoisting, and sinkers 
should not be allowed to ride in them. 

67. Rope Hooks and Bridle 
Chains. —The hoisting rope is usually 
attached to the bail of the bucket by a spe¬ 
cial hook provided with a clip or extra link 
and pin for securing the hook fastening 
while the bucket is being hoisted, as shown 
in Fig. 16 (a) ; or two hooks are arranged 
with a drop link, as shown in Fig. 16 (&). At times, bridle 
chains are used, the hoisting rope being attached permanently 
to the bridle chain by a socket, as in Fig. 16 (c), or a clevis, as 
in Fig. 16 ( d ). 



68. Guides for Buckets. —When the bucket has a ten¬ 
dency to revolve while being hoisted from a deep shaft, the 




difficulty may be overcome by the use of a yoke and guides. A 
simple form of this kind, known as a rider, and shown in 



































DRIFTS, SLOPES, AND SHAFTS, PART 1 39 


Fig. 17, consists of a cross-bar connecting two vertical legs, the 
upper and lower ends of the legs being provided with eyes d 
loosely embracing the guide ropes c. These guide ropes are 
either coiled on a drum and lowered as the sinking proceeds, or 
are hung from the timbers across the top of the shaft. Large 
weights are attached to the lower ends to keep them steady. 
At the bottom of the shaft timbers stop-blocks h hold the rider 
while the bucket goes to the bottom of the shaft, thus keeping 
the rider and the guide ropes out of the way of the sinkers. 



As the bucket is hoisted, the rope socket picks up the rider 
when it is reached. Considerable time is lost in steadying 
the bucket before it goes up and down, unless some such rider 
is used. 


69. Fig. 18 shows a form of yoke that slides on guides the 
same as a cage. In each crosspiece of the yoke, there is a 
ferrule through which the rope passes, the bottom ferrule being 
conical to receive the cone on the rope socket. At the bottom of 
the timbering, two blocks are bolted on each side of the guides 

















40 DRIFTS, SLOPES, AND SHAFTS, PART 1 


to prevent the yoke from descending below the timbers, while 
the bucket passes down to the bottom of the shaft. 

In using yokes or crossheads, great care should be taken to 
have the guides parallel and with good joints, for many acci¬ 
dents have occurred from the crosshead sticking and hanging 
in the shaft, while the bucket continued to go down. If the 
hanging crosshead jars loose after the bucket has gone 50 or 

the bucket, it may carry it to 
the bottom. This is more 
likely to occur in lowering 
men than when lowering the 
empty bucket, for in the lat¬ 
ter case the lowering is 
quickly done, taking the 
crosshead past the tight 
spots. 

Cages are sometimes used 
in sinking, in which case 
false guides must be put in 
from the lower end of the 
permanent timber to the bot¬ 
tom of the shaft. As these 
guides must be removed be¬ 
fore each blast, and then re¬ 
placed, the use of cages is 
not favored. 


70. Shaft Coverings. 
In order to prevent material 
falling into the shaft, the top 
should be covered with 3-inch or 4-inch plank, excepting the 
portion that must be left open for the passage of the hoisting 
bucket. This opening may be simply covered by the larry, as 
shown in Fig. 21; but it is better to have a pair of doors meet¬ 
ing in the middle and closing down flat, or as shown in Fig. 19. 
In the lowered position, they rest on a triangular boxing at 
each end and may be so arranged that the ascending bucket 
will open the doors for its own passage, while they are closed 


100 feet below, and then falls on 



































DRIFTS, SLOPES, AND SHAFTS, PART 1 41 


by means of weights not shown; or the doors may be opened 
and closed by the levers shown in the figure. The balance 
weights should not be hung inside the shaft as is sometimes 
done, for if the ropes break they will drop to the bottom. 
When the doors are closed, the hoisting rope passes through a 
small hole cut in the two edges of the doors. 



71. Dumping: the Buckets.— At the top, the bucket 
may be dumped automatically by placing a catch hook so that it 
engages one side of the bucket rim and tips it as the hoisting is 
continued, dumping the material either into a chute or into a 
car. Any method of 
dumping the bucket 
while over the shaft 
is dangerous, as small 
stones may fall down 
the shaft through the 
hole provided for the 
hoisting rope. It also 
throws a considerable 
strain on the head- 
frame, hoisting gear, 
and rope; and if an 
accident occurs to the 
hoisting rope while 
dumping, the bucket 
and its load may fall on 
the shaft cover with 
sufficient force to break through and fall to the bottom. A 


better arrangement is to swing the bucket clear of the shaft by 
means of a short snatch rope that hangs from a point in the top 
of the head-frame and at one side of the shaft opening. The 
hook is quickly put into the bail of the bucket as it comes up, 
and when slack is given by the engineer, the bucket is swung 


clear of the shaft and dumped or transferred to a car. 

Several buckets are often used for hoisting material, and as 
soon as the bucket has passed through the shaft opening, a 
larry, or truck, running on a broad track that spans the shaft 






















42 DRIFTS, SLOPES, AND SHAFTS, PART 1 


opening is pushed underneath it, the bucket is lowered onto 
the larry, the hooks are snapped, and an empty bucket attached 
in its stead. The larry is then moved to one side and the empty 
bucket lowered into the shaft. 

The larry, or truck, is a low flat car similar to that shown 
in Fig. 9 but without sides. An old railroad hand car that has 
had its axles made to fit the gauge of the track is often used. 

72. Hoisting’ Engine. —The hoisting engine used in con¬ 
nection with the sinking is either a special engine that forms 
part of the shaft sinker’s outfit and can easily be moved from 
place to place, or any engine that can be readily had and used 
until the shaft or slope is finished, when it is dismantled and 
disposed of to the best advantage. 

A second-motion engine is safer for sinking purposes than 
a first-motion engine, as it is not so quick and positive in its 
movement of cages or buckets and the engine can be run rap¬ 
idly with less danger to the sinkers. A good hoisting engine 
should be able to pick the bucket off the bottom at any time, 
without getting stuck on center or having to run back for slack. 

The engines for sinking are usually placed on a temporary 
foundation made of heavy timbers. The tower backstays are 
sometimes used as part of this foundation, though this is not 
good practice, as they may move. 

73. Portable Boiler.— A portable boiler of the locomo¬ 
tive type is generally used, and the engineer frequently does his 
own firing. When a second shaft is sunk within 300 to 400 
feet of the main hoisting shaft, steam is sent direct to the 
sinking engine at the second shaft through a pipe large enough 
to prevent excessive condensation. A steam separator is used, 
or the steam pipe is covered, to reduce condensation. Some¬ 
times a steam separator is used in connection with a covered 
steam pipe. 


HEAD-FRAMES AND OTHER SHAFT STRUCTURES 

74. Sinking Head-Frame.— When an air-shaft or 
escape shaft is supplied with cages or a bucket for hoisting, 
the sinking tower, or head-frame, may be left in place after 



DRIFTS, SLOPES, AND SHAFTS, PART 1 43 


the shaft has been sunk. Otherwise, the head-frame is designed 
for temporary use only. It is usually built of 8"X8" or 
10"X12" pine timbers that are mortised and cross-braced, or 
tied, with heavy iron rods. Fig. 20 shows an unusual form of 



sinking head-frame that was used in sinking one of the largest 
shafts ever sunk; the shaft was 12 ft.X54 ft. in cross-section. 

Sinking frames are sometimes built of 2J"X2J" angle iron; 
in some cases these are cheaper than those made of timber, as 
they are put together with bolts and rivets, which can be easily 
removed with less damage to the parts than in the case of a 
timber frame put together with mortise and tenon. Railroad 


































































44 DRIFTS, SLOPES, AND SHAFTS, PART 1 

rails are laid across the shorter dimension of the shaft mouth 
midway of its length for a larry track. 

Ordinarily, the towers are from 20 to 30 feet high and carry 
on top a single sheave of from 6 to 8 feet in diameter, so 
arranged that the bucket will hang in the center of the shorter 
dimension of the shaft. Instead of using a head-frame, a 
derrick is frequently used, at least until after the shaft has 
been sunk through the surface wash. 

75. Temporary Head-Frame. —In order that the work 
of sinking may not interfere with the progress of the per¬ 



manent work about and over the shaft, such as the erection of 
the main tower, or head-frame, and the building of the foun¬ 
dations for the permanent hoisting engine, buildings, etc., the 
temporary hoisting engine should be located at one end of the 
shaft (at the end opposite the manway if possible), as shown in 
Fig. 21, which gives a side and an end view of a temporary 
head-frame. This shaft is to be a three-compartment shaft, 
having two hoisting compartments and a manway. The man¬ 
way is divided from the hoisting compartments by a close par- 




























































DRIFTS, SLOPES, AND SHAFTS, PART 1 45 


tition of heavy timber. The buntons separating the two 
hoistways are put in later, or when the sinking is completed. In 
the side view, Fig. 21, the head-frame is shown set on the 
cross-sills, just inside the main sills, so as not to interfere with 
the erection of the outer posts of the permanent head-frame. 
By this arrangement, the hoisting of the excavated material 
may continue uninterrupted while the permanent head-frame 
and buildings are being erected. 

The waste material hoisted out of the shaft is dumped about 
the shaft frame and about the foundations of the permanent 



machinery and a level surface is thus gradually built up. If 
the ground slopes away rapidly from the shaft, it may be 
necessary to build a trestle for the larry track. A smaller car 
is sometimes placed on a larger truck and run out on a trestle 
at right angles to the main dumping trestle. 


431—4 



















































































46 DRIFTS, SLOPES, AND SHAFTS, PART 1 


76. Ventilation. —An air-shaft of boards is erected over 
the manway at the surface, as shown in Fig. 21; this serves the 
double purpose of protecting the manway and ventilating the 
shaft, as a natural current is produced in the shaft. The parti¬ 
tion separating the manway from the hoistway should be kept 
close to the bottom of the excavation. If this does not pro¬ 
vide sufficient ventilation, a steam jet or small blower, such 
as is used in a blacksmith’s forge, may be used. 

77. Manway or Pumpway. —When the small compart¬ 
ment at the end of the shaft is used as a manway, it is 



Fig. 23 


equipped with stairways. Fig. 22, inclined ladders, Fig. 23 (a) 
and ( b ), or vertical ladders. The mining law in some states 
provides that such stairs or ladders shall not have an inclination 
steeper than 60°, and that proper landings shall be made at 
the top and bottom of each flight of stairs. Vertical ladders 
are particularly dangerous. The ladders are sometimes 
arranged one above another, with a suitable staging or plat¬ 
form connecting the top of each ladder with the foot of the 





























































DRIFTS, SLOPES, AND SHAFTS, PART 1 47 

next ladder above, all the ladders being inclined in the same 
direction, Fig. 23 (a) ; sometimes they zigzag across the shaft, 
the foot of one ladder being placed alongside the top of the 
ladder below it, as in Fig. 23 ( b ). 



METHODS OF LIGHTING AND DRAINAGE 

i 8. Lighting:. —As sinking operations are frequently con¬ 
tinuous, day and night, some good form of artificial light is 
essential at the top as 
well as at the bottom 
of the shaft; water¬ 
proofed incandescent 
lamps are most satis¬ 
factory. A group of 
these protected by a 
metal basket forms by 
far the most conve¬ 
nient method of light¬ 
ing the bottom, as 
they give ample illu¬ 
mination and can be 
easily hoisted out of 
the way during blast¬ 
ing and can also be 
easily run up and 
down the shaft for an 
examination of t h e 
timbering. Electric 
lights do not load the 
air with the impure fumes that come from the ordinary miner’s 
lamp, especially where kerosene oil is burned. Also, the water 
dripping down the shaft causes an incrustation to form on the 
wick of a miner’s lamp, which must be removed constantly in 
order to maintain a good light. The top of the shaft should 
be provided with a strong and steady light, and for this pur¬ 
pose a protected lamp or lantern with a good reflector should 
be used. 


Fig. 24 





48 DRIFTS, SLOPES, AND SHAFTS, PART 1 


79. Drainage. —Surface water is kept out of the shaft 
by banking about the shaft sill the clay and other material 
taken out during the sinking. The water pumped or hoisted 
from the shaft is carried away in tight wooden troughs that 
lead in the direction in which the surface dips, and extend far 
enough from the shaft to prevent the water from returning. 
During the sinking, a hole, or sump, is excavated at one end or 
in the center of the shaft somewhat in advance of the general 
work. The water is either bailed out of this hole and hoisted 
in buckets, or a sinking pump of special form is employed. 
These pumps may be hung by hooks from the timbering, as in 
Fig. 24, at any point or simply hung by ropes, and may be 
hoisted and lowered as desired. Instead of a special sinking 
pump, a small horizontal pump of ordinary pattern is often set 
up on a temporary staging, which is moved downwards as the 
work advances. Either of these pumps is connected with the 
steam and water pipes in the manway by short lengths of wire- 
wound rubber hose. 


DRIFTS, SLOPES, AND SHAFTS 

(PART 2) 

Serial 846B Edition 2 


SHAFTS — (Continued) 


WORK OF SINKING 


PREPARATORY WORK 

1. Supply of Material and Appliances. —Before the 
actual sinking of the shaft begins the preparatory work is of 
vital importance. All materials and appliances that are liable 
to be required, or at least a sufficient supply for immediate 
need, should be on the ground and ready for use before the 
excavation work is begun. Prospect holes or shafts located in 
the vicinity, as well as a geological cross-section of the tract, 
will give the needed information about the character of the 
strata to be penetrated. These data will also help to determine 
the kind of material and appliances that will be required. 

2. Position of Shaft. —A suitable site for the shaft hav¬ 
ing been selected and a plan of the surface tracks and connec¬ 
tions having been submitted, and approved by the railroad 
company, the exact position is staked out by driving eight stakes 
a, b, c, d, e, f, g, h in line with the ends and sides of the shaft 
and outside the area likely to be disturbed by the sinking 
operation, as shown in Fig. 1. These stakes are located with 
a transit so that the lines a d and h e are parallel and at a dis¬ 
tance from each other equal to the width of the shaft. The 
lines b g and c f are also parallel to each other and at right 


COPYRIGHTED BY INTERNATIONAL TEXTBOOK COMPANY. ALL RIGHTS RESERVED 





50 DRIFTS, SLOPES, AND SHAFTS. PART 2 

angles to the lines a d and h e. The distance between the lines 
b g and c f is equal to the length of the shaft. If cords are 

stretched between opposite 
9® stakes so as to occupy posi¬ 

tions as indicated by the 
dotted lines, the points of in¬ 
tersection i, 2 , 3 , 4 indicate 
the four corners of the 
shaft. By measuring the 
distances a i, b i, c 2 , d 2 , 

e 3>f 3> 9 4> h 4> the P oints 
/, <?, 3 , 4 can be checked at 
any time by measurement 
from any two of the permanent stakes, or they can be located 
by sighting with the transit and measuring from any of the 
fixed stakes. 

If the shipping tracks are near the shaft, the long side of the 
shaft should be made, as nearly as possible, parallel to these 
tracks. If the seam to be developed is inclined, the long side 
should be, as nearly as possible, parallel to the line of dip of 
the seam. 

3. Shaft Templet, or Sill. —After the shaft has been 
staked out, shallow trenches are dug on each end line in which 
are laid the end sills, or cross-sills, which extend from 6 to 
8 feet outside the shaft line on each side. Similar side sills, or 
main sills, are then laid 
across the end sills; these ex¬ 
tend from 4 to 5 feet beyond 
each end line, as shown in 
Fig. 2. 

These timbers are usually 
of carefully selected 12"X 12" 
or 12"X16" oak. Square 
boxings from J inch to 2 
inches deep are cut in the 
upper faces of the end timbers and in the lower faces 
of the side timbers and a drift pin is inserted at each corner 
















DRIFTS, SLOPES, AND SHAFTS. PART 2 51 


to pin the sills together. The length of the long tim¬ 
bers between the notches, or boxings, is equal to the clear 
length of the shaft, and that of the cross-timbers between the 
notches is equal to the clear width of the shaft, so that these 
timbers form a templet for the size of the shaft in the clear 
for all future excavation. When these timbers are laid in 
position, instead of being laid in trenches or on the surface of 
the ground, the sills are frequently raised and clay dumped 
about them to a sufficient height to prevent surface water 
running into the shaft. The timbers thus raised are supported 
on blocking and carefully leveled and squared. The work of 
sinking and the methods of timbering vary greatly according to 
the character of the ground and will therefore be treated under 
separate headings. 

SINKING THROUGH GROUND THAT DOES NOT RUN 

4. First Stage of Excavation.— The excavation is 
started with pick and shovel by throwing the material from 
within the timber frame or 
sills. The earth is excavated 
a sufficient distance from the 
face of the timbers all around 
the shaft to allow the face of 
the shaft lining to be set flush 
with the face of the sills. The 
face of the timbers is the ex¬ 
posed surface on the inside 
forming the face of the shaft 
when timbered; the surface 
against the strata is called the 
back of the timbers. The 
excavation is carried down 
without timbers to support the 
side and end walls, as far as 
is considered safe, when the work is squared and the curb¬ 
ing, or shaft lining, put in place. The depth thus excavated 
without supporting timbers will depend on the nature of the 
ground and will vary from 6 to 20 feet. With a long-handled 







52 DRIFTS, SLOPES, AND SHAFTS, PART 2 


shovel, a man can generally throw the dirt to the surface from 
a depth of 10 feet, after which a temporary staging must be 
erected, similar to that shown in Fig. 3, on which the dirt is 
thrown and thence to the surface. The pick used is the 
ordinary heavy dirt pick with wide point, while the shovel 
is the round-pointed D-handled shovel; when the material is 
thrown to a considerable height, a long-handled shovel is 
used. Wedges may be employed for wedging loose sandstone 
and slate from the bottom and for trimming the sides and 
ends of the excavation, but no powder is used. The walls 
and corners of the shaft are neatly trimmed and carefully 
watched for any sign of yielding, as the excavation must 
not be carried unsupported far enough to cause any caving, 

bulging, or weakening of the 
ground about the head of the 
shaft. 


5. Plumbing: the 
Shaft. —As it is important 
that the shaft be kept verti¬ 
cal, a plumb-line b c, Fig. 4, 
is usually suspended from 
each corner of a rectangular 
shaft, or from the center of a circular shaft. It may be hung 
from a block b, spiked in the corner of the sills, or from a 
cast-iron plate about 1 foot square screwed on one of the 
sills at one corner, the plumb-line passing through a small 
hole in the plate. It is arranged so as to hang 4 or 6 inches 
from the face of the shaft timbers. In excavating the earth, 
or in setting the shaft lining, measurement is made from these 
lines, allowing, when excavating, for the thickness of the wall¬ 
ing or timbers forming the shaft lining. Thus, if the plumb- 
lines are hung 4 inches from the face of the shaft, and the 
thickness of the shaft lining is 6 inches, a measurement of 
10 inches will clear the timbers. It is customary, however, 
to allow about 2 inches behind this to insure clearance at all 
points, as time is saved in the setting of the timbers by so 
doing. 



















DRIFTS, SLOPES, AND SHAFTS, PART 2 53 


G. Lining' the Shaft. —In lining the shaft, the walling, 
or timbering, is often built up in sections from the bottom of 
the excavation as the sinking progresses, the space behind being 
filled with sand or other fine material that will distribute the 
pressure evenly over the lining. In wet strata, the space 
behind the walling should be well rammed with clay to prevent 
the inflow of silt or fine sand between the timbers. Except 
when sinking in rock, the shaft lining must be kept within 




Fig. 5 

a short distance of the bottom of the excavation; this distance 
depends on the character of the strata, but seldom exceeds 
6 or 8 feet except in unusually firm ground. The work of 
excavating is thus carried on in short stages, alternating with 
the work of extending the shaft lining. 

7. Sinking Through Rock. —As soon as the strata 
become hard or firm enough to hold the explosive charge, 
powder is employed and percussive, hand, or machine drills 




















54 DRIFTS, SLOPES, AND SHAFTS. PART 2 


are used, the type of drill depending on the character of the 
rock. In soft rock, a hand percussive drill is used and a light 
lifting shot is employed to dislodge the material from its bed. 
This material is afterwards broken by wedges and hammers or 
sledges. For this class of work, a slow large-grained powder 
is required. A quick powder exploded in soft material will 
find vent by a single rupture of the strata without exerting 
the lifting force on a great mass of material, as is done when 
a slower powder is used. If, however, the strata are full of 
seams and cracks, a small charge of a quick powder is used, 
since such rock will not confine the explosive force sufficiently 

to do effective work when a slow 
powder is used. In hard rock, 
dynamite is used, and power drills, 
operated by compressed air or 
steam and usually mounted on shaft 
bars, are emoloyed. 


.rase 


20 - 

P/an of //. ft. Cut 



Fig. 6 


8. Location of Holes. —The 
general position of the holes and 
their depth are about the same as 
described under Tunneling, in 
Drifts, Slopes, and Shafts, Part. 1. 
The first shots in a level floor should 
be inclined at a fairly sharp angle 
with the floor, and are usually cen¬ 
tral in the shaft. These holes are 
often called sumping holes; their purpose is to start the excava¬ 
tion by blowing out a wedge-shaped piece of rock from the 
center of the floor. The holes are generally arranged in series, 
or rows, on each side of the center and across the width of 
the shaft, and are spaced an equal distance from one another. 
The general position of these holes is illustrated in Fig. 5, 
which also shows the position of the shaft bar on which the 
drills were mounted. The dimensions given are those that 
were employed in the sinking of a shaft in a white crystal¬ 
line limestone. In this shaft, at first, only 6-foot cuts were 
made, a single series of shots excavating the material to this 








DRIFTS, SLOPES, AND SHAFTS, PART 2 55 


depth. The depth of the cut, however, was afterwards greatly 
increased by boring the side holes deeper, as shown in Fig. 6, 
until the cuts averaged 11 feet, six successive cuts excavating 
the shaft a depth of 66 feet. 

9. Method of Drilling, Charging, and Firing 
Holes. —An example taken from the southeastern Missouri 
lead region illustrates the sinking of a 6'X18' shaft in lime¬ 
stone of varying hardness. The position of the shaft bar on 
which the drills were mounted is 
shown at a, a x , a 2 , b, b l9 b 2 , in the 
lower view of Fig. 7, which is a 
sectional elevation, the upper 
view being a plan. The two 
center rows of holes, I, or the 
sumping holes, were drilled first, 
and each hole filled with from 
five to seven -§-pound sticks of 
giant powder or dynamite, con¬ 
taining 50 per cent, of nitro¬ 
glycerine. The depth of the 
holes varied from 3J to 6 feet. 

Beginning at the center, the suc¬ 
cessive rows of holes, marked 
j, 2 , 3 , and 4 , respectively, on 
both sides of the center line of 
the shaft, were drilled, charged, 
and fired in pairs, the material 
being loaded and hoisted between 
each operation. The end holes required but four or five 
sticks of 40-per-cent, dynamite apiece; the entire cut of 
twenty-six holes used from 50 to 60 pounds of dynamite, 
and excavated the material to a depth averaging from 3| to 
6 feet. The average quantity of 40- and 50-per-cent, dynamite 
in this material was 12 pounds per foot of depth, or 3 pounds 
of dynamite per cubic yard of excavation. The sinking was 
carried on by three shifts of four men each, and the record of 
the sinking showed a depth of 100 feet in 30 working days. 







56 DRIFTS, SLOPES, AND SHAFTS. PART 2 


The record of the sinking of a shaft at Rossland, British 
Columbia, shows an average of 25 pounds of dynamite per 
foot of depth in a shaft 9 ft.X20 ft., or practically 4 pounds 
of dynamite per cubic yard of material excavated; the rock 
in this case was a hard, igneous formation composed mostly 
of diorite. These examples illustrate the practice of sinking 
in rock in different localities. 


\9b 

i 

i 

• b 

~9b~ 


‘*1 

f 

i 

\9b 

1 

| 

9a 

9a 

9a 

1 

b9\ 

1 

!•* 

i 

9a 

•a 

9* 

&•! 


_j9b _ 

_ 9b _ 

9b _ 

aJ 



Fig. 8 




10. Tlie Long-Hole, or Continuous-Hole, Method. 

As in sinking in rock much time is ordinarily lost in drilling, 
and as machine drills cannot work close to the sides, ends, 
or corners of the shaft, the continuous-hole method is 
sometimes used. By this method, a number of diamond-drill 
holes are put down at definite distances apart, and from 100 

to 300 feet deep, over the 
area where the shaft is to be 
sunk. They are arranged in 
rows, from 3 to 4 feet apart, 
with the outside rows close to 
the sides and ends of the 
shaft, so that they will nearly 
square it up and save much 
digging and trimming. They 
are then filled with sand or water, preferably the former. The 
sinkers prepare for the work of blasting by removing 3 to 4 
feet of the sand from the holes and filling this space with 
explosives, which are tamped and fired. 

Fig. 8 shows how the holes are arranged. The holes 
marked a are first cleaned and fired to give a loose end to the 
holes b on the outside, which are next cleaned out and fired. 
This work is continued until the bottom of the hole drilled by 
the diamond drill is reached, when another series of long holes 
is drilled. 

This method probably originated from one that is sometimes 
used in the coal fields of the Central Basin. The shaft is sunk 
about the diamond-drill hole that was drilled for prospecting 
purposes. The sinkers charge a section of the hole, using a 
false bottom, and blow out a center cut. 


DRIFTS, SLOPES, AND SHAFTS, PART 2 57 


11. When shafts are sunk to workings already opened, a 
diamond-drill or churn-drill hole is sometimes put down into 
the open works below, and this hole kept open during sinking, 
thereby avoiding all hoisting of water. A long chain is used to 
clean out the hole when it becomes stopped up. 

Both this plan and the long-hole plan are apt to cause crooked 
shafts on account of the divergence of the drill hole from the 
vertical. The advantages of the long-hole system are that 
sinkers need not wait while holes are being drilled ; and blasting 
can be done as soon as debris from shots is removed. The 
method is said to be very much quicker than the ordinary prac¬ 
tice of using power drills driven by air or steam, but is more 
expensive. 

12. Shaft Lining-.— Timbering is usually not required 
for securing the sides of the excavation when sinking in hard 
rock. Cross-buntons to support the cage guides, pipes, wires, 
etc. are set in hitches in the face of the rock, and are spaced 
6 or 8 feet apart. They are carefully lined and placed verti¬ 
cally over each other and then tightly wedged. In sinking 
through soft shale or loose crumbling rock, a greater amount 
of timber is needed for securing the sides. The sides are 
trimmed with the pick; and when the material is dry, a close- 
fitting lining of 3-inch or 4-inch planking is sufficient, the thick¬ 
ness of the planking increasing with the depth of the excava¬ 
tion. In wet material, 4-inch timber should be used at the 
surface, 6-inch at 100 feet, and 8-inch at 200 feet. 

13. Sinking in Swelling Ground. —Clay or marl that 
swells when brought in contact with air and water is difficult 
to excavate and support. There is no timbering that can 
resist this swelling; it will burst any timber or break any 
frame that can be put in. In sinking a shaft or a slope under 
such conditions, the strata should be excavated for a certain 
depth back of the lining so as to give a good clearance between 
the formation and the lining all around the shaft. This space 
should be so arranged that a man can enter it and clear it from 
time to time as may be required. Drainage should be provided 
by cutting, in the hard pan or floor underlying such strata. 


58 DRIFTS, SLOPES, AND SHAFTS. PART 2 


a ditch connected by a pipe with the sump at the foot of the 
shaft. A good circulation of air should be made to travel 
around the space thus excavated so as to keep the clay as dry 
as possible. 

The method of sinking through such ground does not differ 
materially from that used in other loose ground or rock, but 
the timbering of the excavation is of great importance. 


SINKING THROUGH QUICKSAND OR RUNNING GROUND 

14. Nature of Quicksand.—Quicksand is sand that 
is so impregnated with water as to be semiliquid and therefore 
shifting and easily movable. Instances are on record where 
beds of quicksand were practically continuous for a depth of 
75 feet, and as the semifluid material is often under great 
pressure, it sometimes bursts forth with great violence as the 
excavation approaches it, giving the sinkers barely time to 
escape. The bottom of the excavation may fairly boil, while 
the fluid material may rise several feet in the shaft. In differ¬ 
ent localities, as in the Wyoming Valley of the Pennsylvania 
anthracite region, and in Central Illinois, these deposits occur 
in buried valleys of considerable extent, and sinking shafts in 
them by the ordinary methods is impossible. These conditions 
render sinking extremely hazardous, especially when they 
occur at a depth of from 50 to 100 yards below the surface. 

15. Precautionary Measures. —The risks involved in 
meeting deposits of quicksand make it all the more important 
that the strata should be thoroughly prospected previous to 
sinking, and in localities where such deposits may be expected 
it is particularly important to have on hand an ample supply 
of the materials required during sinking. Timber of different 
sizes should be framed and ready for instant use, and pumps 
and piping of the proper kind and capacity should be on hand. 
Eight or ten pointed pipes, with perforated ends, are some¬ 
times driven into the sand 6 or 8 feet apart and connected 
at their upper ends to a suitable pump. In some cases, a few 
hours’ pumping draws off the water and the boiling sand settles 



DRIFTS, SLOPES, AND SHAFTS, PART 2 59 


and solidifies so that it may be removed with a shovel. Water 
can sometimes be drained from the soft ground within the 
area of the shaft into wells or small temporary shafts sunk 
adjacent to the larger shafts, thus leaving the sand within the 
shaft area compact and easily removable by shoveling. 

16. When the watery sand is thus drained, there is a con¬ 
siderable decrease in volume of the material surrounding the 
sides of the shaft; the shaft lining is thus frequently robbed 
of all supporting material for a considerable distance up the 
shaft and begins to separate and sag, while the shaft may be 
swung out of line. This decrease in volume, or displacement 
of the strata, due to the draining off of the water, may be 
carried to such an extent that the surface of the ground 
will sink several feet over a large area surrounding the shaft. 
In removing the water, a large amount of sand is also removed; 
the effect of its removal is often not appreciated until too late. 
The sand contained in the water will often cut out the pump 
linings in a short time, and render the pump useless; but if a 
layer of straw or other light material is thrown into the shaft, 
it will form a mesh by which the sand will be largely filtered 
from the water. 

The methods to be adopted when sinking through such mate¬ 
rial are particularly methods of timbering, or supporting, 
the sides of the excavation; and the excavation must be kept 
timbered close to the bottom of the shaft. There are, however, 
certain methods of sinking that are particularly applicable 
to such ground, as follows: the use of cement, piling, fore- 
poling, the use of shoes, the pneumatic process, and the freezing 
process. 

17 Consolidating- Sand with Cement. —The shifting 
sand or loam in water-bearing strata may be consolidated by 
injecting powdered cement -into the soft ground by means of 
compressed air, steam, or water under pressure. The cement 
is first screened in order to free it from lumps, and the powder 
is taken by an injector that forces it through a flexible pipe 
into a perforated tube sunk in the soil to the required depth. 


60 DRIFTS, SLOPES, AND SHAFTS, PART 2 


18. Sand Beds Excluded by Piling:. —A bed of quick¬ 
sand or other soft material lying near the surface is often best 
treated by piling. If the bed is shallow, it may be sufficient 
to drive a single set of piles all around the site of the proposed 
shaft. Where thicker beds of quicksand occur, it may be 
necessary to drive several series of piles, each successive series 
being driven inside the former after the material has been 
excavated to a point near the bottom of the first piles driven. 
The second set of piles having been driven, the material 
within these is excavated to a point near the bottom of the 



piles, and, if necessary, a third set of piles is driven within 
the second. This method is illustrated in Fig. 9. 

After the first set of piles a has been driven, they should 
be supported against external pressure, as the material is 
excavated from the space they enclose, by timber frames or 
timber sets at their top and middle. It is important that these 
frames should be set promptly and braced by cross-buntons 
supported by punch blocks e. As will appear from the illustra¬ 
tion, it will be necessary to set the first sets of piles a sufficient 
distance back from the shaft to allow for the decreasing dimen- 






































DRIFTS, SLOPES, AND SHAFTS, PART 2 61 


sions of the excavation, as each series of piles is driven. The 
required distance is easily calculated when the depth of the 
sand bed is known, and this information has already been 
obtained from the drill hole t. 

19. In some cases, the soil at the surface may be firm for 
a considerable depth, but underlaid by a flowing bed of quick¬ 
sand. In this case, the excavation of the overlying soil may be 
done in the usual manner, and after this is lined or curbed 



Fig. 10 


the piles may be driven from the foot of the excavation in 
the same manner as from the suiface. In this system of 
sinking through watery strata, the permanent shaft lining is 
built up as soon as the rock is reached. The space between the 
shaft lining and the piles is then filled with clay, where this can 
be obtained, or the timbers are backed with a sufficient thick¬ 
ness of cement, and this, in turn, with the material excavated. 

431—5 






















62 DRIFTS, SLOPES, AND SHAFTS, PART 2 


20. Forepoling in Quicksand. —The method of fore- 
poling, described under Tunneling in the preceding Section, 
may also be applied for sinking through quicksand, as shown 
in Fig. 10. Strong timber sets j are framed to the sides of the 
shaft. As each set is put in, it is suspended from the next one 
above, as the set a, by light strips, or lath, /, while the punch 
blocks b are set between the frames to hold them apart. Two- 
inch planks with the ends sharpened are used for the spiles k , 
and are driven downwards in an inclined position behind the 
lower timber set. Before driving the spiles, the tail-pieces C 
are spiked to the lining just above the lower timber frame; the 
spiles are then driven as the excavation advances until their 

tops reach this tail-piece. An¬ 
other set of timbers is then 
placed in position at the floor 
and tied to the timbers above, 
and the same operation repeated, 
driving the spiles and excavating 
the material as rapidly as pos¬ 
sible. This process of fore- 
poling may be carried on at any 
depth below the surface where 
the strength of the timbers will 
resist the pressure of the sand. 

21. Another method of fore- 
poling, adapted to a greater 
depth below the surface and a 
greater thickness of sand, is 
illustrated in Fig. 11. This method is similar to that last 
described, except that the spiles are driven in at a greater 
inclination. The timber frames, however, are placed somewhat 
closer and no tail-piece is employed, the tops of the spiles 
bearing against the timber above instead of against the tail¬ 
piece. 

22. Fig. 12 illustrates the use of breast boards where the 
bottom has a tendency to rise and fill the shaft, and must be 
planked to keep it down. The material is removed a little at a 


a 
































































































































DRIFTS, SLOPES, AND SHAFTS, PART 2 63 


time. A sump is carried ahead of the regular excavation, as 
shown, by driving short piles and putting in a small frame. 
The work is slow and tedious, and requires great care and 
caution. 


23. In another system of forepoling interlocking channel 
bars are used in the manner shown in Fig. 13. In this system 
the shaft is started with dimensions that are 2 feet larger each 



Fig. 12 

way than the size required, and is sunk in the ordinary manner 
down to the sand; thus, an 8'X16' shaft must be started as 
10 ft.X18 ft. 

As seen from Fig. 13, the sides of the lining are composed 
of channels a and b alternately facing inwards and outwards. 
The channels a have Z bars c riveted to them, which engage 
and interlock the edges of the channels. The channels b 
have angle irons d riveted to them, thus forming grooves 
in which the sides of the channels a run. The corners of 
the shaft lining are made of three angles e riveted together, 
as shown, which interlock with the side and end channels a 
by means of the Z bar riveted to a. Heavier sections can be 





































































64 DRIFTS, SLOPES, AND SHAFTS, PART 2 

used, which would make the thickness of the metal about 
i inch. When sand is reached, these channels are set plumb 
in a solid frame inside of the shaft lining, and are driven 
vertically downwards through the sand to the solid material, 
if possible, before any sand is excavated. No one channel 
should be driven more than 2 feet ahead of the rest. A perfect 
fitting anvil, or clinker, is used to protect the head of the 
channel bar while driving. Channels 12 feet long are readily 
driven their entire length into the sand. 

24. Channel sheathing can be driven in varying depths 
by feeding in pieces from the top, thus driving the preceding 



Fig. 13 


one down, in the same manner that a follower is used in driving 
piling. The individual members, engaging and interlocking, 
slide on each other so that one can be driven at a time, and thus 
afford an opportunity to drive channels all around a boulder, 
should one be encountered. The channels interlock nearly 
water-tight, and, by cementing above and below them, the 
water may practically be shut off. The channel lining may 
be assumed to be 5 inches thick, while 6 inches should be 
allowed for the timber. The channels are either left as a 
permanent lining or they may be drawn after a timber lining 
has been laid. They are cheaper than steel shoes, or drums, 
subsequently described. 







































































DRIFTS, SLOPES, AND SHAFTS. PART 2 65 


25. Shoes for Shaft Sinking. —The iron or wood 
structure known as a shoe has in its various forms been well 
known for many years to engineers and contractors in con¬ 
nection with excavating work. It consists of a frame corre¬ 
sponding in shape to the cross-section of the shaft. Attached 
to its bottom is the cutter, which is of steel and beveled so that 
it will sink easily into loose ground. The shoe is usually open 
top and bottom, but sometimes so arranged that the top can be 
closed tightly with steel plates, to resist the sand pressure 



Fig. 14 

from the shaft bottom. The upper part of the shoe is outside 
the shaft lining from 12 to 16 inches, and the lower part is 
usually divided into compartments by braces that brace the 
sides and ends. 

In principle, the plan of sinking by a shoe is similar to the 
method of tunneling in soft ground with the use of an advance 
shield, except that shaft shoes, in America, are usually rec¬ 
tangular in shape, while the shield in tunnel driving is cylin¬ 
drical. As the material is excavated from beneath the shoe, 









































































66 DRIFTS, SLOPES, AND SHAFTS, PART 2 


the shoe drops by its own weight or on account of pressure 
applied to its upper surface by weights laid on it or by means of 
jacks, generally the latter, thus walling back the sand while the 
lining is being put in place. Only enough material is excavated 
from underneath the shoe and it is moved just far enough 
ahead to permit the placing of one set of timbers at a time; if 
planks are used for the shaft lining, they are put in flatwise. 
The shoe should descend uniformly at all points, and should 
be carefully leveled before the timber is placed. 

26. Fig. 14 shows the plan and elevation of a steel shoe 
that is quite commonly used. It is made of f-inch steel boiler 
plate braced as shown, has a height of 30 inches under the 
shaft timbers, and a sheet-iron lap 18 inches deep extending 
outside of the timbers. Fig. 15 shows it in position at the 
bottom of the shaft, as well as the manner of supporting it and 
controlling its descent. Four hooks, or claws, are provided, 
which may be screwed into the lower coupling c, Fig. 16. To 
each of these hooks is fastened a strong chain attached to the 
frame of the shoe, as shown in Fig. 15; by this means, the 
downward progress of the shoe is controlled, and there is less 
liability of its becoming wedged. 

One of the disadvantages of using the shoe is the fact that 
it is apt to be stopped by boulders, clay seams, or other obstruc¬ 
tions, one part remaining stationary while the other goes down, 
thus throwing the shoe out of level and wedging it so tightly 
that it cannot be moved, and causing the shaft to be thrown out 
of line. Sometimes the shoe is tipped to such an extent that 
it has to be abandoned. By means of the chains shown in 
Fig. 15, this difficulty is partly overcome, as by their use the 
shoe can be held stationary until the obstruction is removed. 
The chain may also be slacked at any time to allow the shoe 
to move. 

The cross-beams of the shoe frame furnish also a good sup¬ 
port for the planks that are used in the shaft lining. As the 
shoe is lowered through a distance of 2 inches, corresponding 
to the thickness of a plank, the latter is slipped into place and 
spiked upwards from beneath, 40-penny nails being used for 


DRIFTS, SLOPES, AND SHAFTS. PART 2 67 


this purpose. The jacks for forcing down the shoe are shown 
in position in Fig. 17. 

The shoe is sometimes forced downwards by the weight of 
the lining, if this rests directly on top of the shoe instead of 
hanging from the top of the shaft. The lining is then built 
from the surface by adding set on set, the increasing weight 
gradually forcing the shoe through the soft material. 

27. Lining- Suspended From Surface Frame. —One 
of the chief difficulties encountered when sinking through sand 



Fig. IS 


beds of considerable thickness is the tendency of the shaft 
lining to settle and draw apart in places, accompanied also, 
very often, with a deviation of the shaft from a vertical line. 
This is caused by the removal of material from the strata sur¬ 
rounding the shaft, due either to the running character of the 
material or to the removal of the water in the sand by pumping 


























































68 DRIFTS, SLOPES, AND SHAFTS, PART 2 


or by drainage. As the lining is robbed of its means of support, 
it will either settle vertically or move laterally, as a result of 
an excess of pressure on one side. To remedy this, the lining 
is often hung from a strong frame at the surface or at some 
point in the shaft where a firm foundation can be obtained. 

28. In Fig. 15 the lining is shown suspended from a 
frame or trussed beam at the surface, by means of steel rods 
coupled to each other in lengths of 10 feet, and supporting at 
each coupling a cross-bunton on which rests the intervening 
lining. The rods may be of any convenient length until the 
sand is reached, when their length should be about 10 feet. 

The diameter of the rods 
may vary from 1J to 2\ 
inches, according to dis¬ 
tance from the surface, 
the size decreasing with 
an increase in depth of 
the shaft. The lower 
end of each section of 
the rods is passed 
through a hole in a cross- 
bunton b, Fig. 16, and 
an iron bearing plate, or 
washer, a, is placed over 
the end of the rod under¬ 
neath the bunton. A screw coupling c is then fitted to the 
end of the rod and screwed in place. This coupling furnishes 
the support for the next section of rod below, which is not, 
however, put in position until the excavation has reached the 
point where another cross-bunton is required. Until this time, 
the timbers of the shaft lining are supported by strips of lath 
nailed to their face, or by being spiked together from under¬ 
neath when flat planks are used. 

29. As an example of a suspended shaft lining the case 
may be cited where a sand bed 50 feet thick was encountered 
60 feet below the surface. For the purpose of supporting the 
lining, four crucible-steel suspension rods capable of sustaining 



Fig. 15 






DRIFTS, SLOPES, AND SHAFTS, PART 2 


69 


a safe load of 132 tons (using a factor of safety of 5) were 

used, one in each cor¬ 
ner of the shaft; the 
length of the first set 
of rods was 20 feet, 
while all the other 
sections were 10 feet 
each. The diameter 
of the rods in the four 
upper sections was 1$ 
inches, that of the 
three next lower sec¬ 
tions If inches, while 
that of the last three 
sections was If inches. 
By this means, the 
hard pan was reached 
at a depth of 110 feet 
from the surface. 
The frame from 
which the rods sup¬ 
porting the lining 
were hung was made 
of 12"X 12" and 12" 
XI6" timbers bolted 
together by drift pins 
to form a truss, as 
shown in Fig. 15. 

A good frame is at 
least 3 or 4 feet high, 
and should extend 
from the shaft to solid 
ground so as not to be 
affected by any move¬ 
ment at the surface 
due to shifting sands, 
as before described. It should be strong enough and sup¬ 
ported in such a manner that it can carry the weight of tower 














































































































70 DRIFTS, SLOPES, AND SHAFTS, PART 2 


and sheaves, as well as the lining, if necessary, although the 
tower should not be placed on the frame if it can be avoided. 

30. The simple frame, shown in Fig. 15, is built directly 
on top of the shaft. The more elaborate one, shown in Fig. 17, 
in elevation and section, is constructed as follows: A 
30 ft.X50 ft. platform of 2-inch plank a is first laid on the 
surface above the shaft. On top of this and running parallel 
to the long side of the shaft are steel rails b (about 60 pounds), 
which form the foundation of the solid timber trusses. Each 
truss shown is made of eight pieces of 12"X12" timber, the 
bottom piece c being 48 feet long and the next d 4 feet shorter, 

and so on to the top one e, 
which is 20 feet in length. 
Across these trusses are 
placed two 16"X16" tim¬ 
bers f, each 20 feet long; 
through these timbers and 
near the inside of the shaft 
walls pass the rods g, cf 
from which the lining is 
suspended. In this case, 
these rods are connected 
by couplings h, shown in 
detail in Fig. 18. The rods 
hold the lining by means of castings a fastened to it by means 
of lagscrews. The shoe, Fig. 17, is hung from the rods by the 
chains k and the swivels /. 

31. Triger, or Pneumatic, Method.— Occasionally, a 
method of sinking is used for shafts and tunnels that is an 
adaptation of the caisson method, used in bridge work, and 
is known as the Triger, or pneumatic, method, as it was 
successfully applied by M. Triger, in France, a number of 
years ago. It has but rarely been used for sinking mine shafts 
and it is necessary, therefore, only to give the principle on 
which it is operated. In this method, a cylinder of cast iron, 
made by successively adding one ring to another at the surface, 
is made to sink slowly into the loose ground, either by its own 



Fig. 18 


































DRIFTS, SLOPES, AND SHAFTS, PART 2 71 


weight, by weights piled on top of the cylinder, or by means 
of pressure applied through jacks. In order to keep out the 
water from surrounding strata, compressed air is led into a 
closed chamber at the bottom of the iron cylinder, the pressure 
of the air being kept just sufficient to prevent an inflow of 
water and loose sand. This chamber forms the working space 
in which the material is excavated; above it, and connected to it 
by suitable trap doors, is another closed space, known as an 
air lock. This air lock, by means of trap doors above and 
below, gives a means of communication between the working 
chamber and the surface. A person enters it through the upper 
trap door; after closing this door he allows the compressed 
air from the working chamber to enter, by means of suitable 
valves, until the air has reached the same pressure as that in 
the working chamber or caisson; the lower trap door, which 
leads into the caisson, is then opened and he descends into 
the working chamber. In order to leave the caisson, the 
opposite procedure is adopted. 

The excavated material can either be removed through the 
air lock, or it can be blown out through a pipe by means of 
air pressure after being mixed with water. If only a few 
boulders are found during the sinking, they are carried down 
in the caisson and are hoisted out after solid material has 
been reached and the roof of the caisson cut away. If many 
boulders are encountered, they must be blasted and the pieces 
hoisted out through the air lock. In some cases, the metal 
casing on top of the caisson forms a sufficient lining for the 
shaft; in other cases, it is necessary to build a lining of timber 
or metal inside of this casing. 

32. Poetscli and Gobert Freezing Processes. —If a 
sufficient thickness of the fluid material of a sand bed is frozen 
to form a substantial wall about the proposed shaft, it is 
possible to excavate the enclosed material. Surrounding the 
shaft, a series of holes, Fig. 19, from 6 to 10 inches in diameter, 
are bored through the sand bed and cased with ordinary well 
casing; or if the sand is very fluid the casing may be driven 
through the sand. These holes if bored from the surface are 


c 


0 0 
0 

--e-— 

0 O 


OO0O00OO 


G 


-e- 


oooooooo 


B 





w\\W\W\m: 







Fig. 19 


72 


















































































































































































































































































































































































DRIFTS, SLOPES, AND SHAFTS, PART 2 73 


usually vertical, but if bored from a point in the shaft a few 
feet above the bed of sand, they are inclined as illustrated in 
Fig. 19. They are not more than 3 to 4 feet apart, in order 
to insure the thorough freezing of the sand between them. 
Inside these casing tubes, smaller ones, usually about 4 inches 
in diameter and closed at the bottom, are let down to the solid 
stratum, and the outer temporary casings withdrawn. The 
4-inch tubes are closed at the top with metal cap pieces, and 
each contains a 1-inch tube that extends almost to the bottom. 
The 1-inch and the 4-inch tubes are connected at the surface to 
circular mains, each vertical tube being fitted with a screw- 
down stop-valve so that it can be cut off from the main. 

33. The Poetsch system is distinguished from the Gobert 
system by the character of the freezing medium. The former 
uses a brine consisting of a solution of calcium chloride (or 
magnesium chloride) passed through a cooling machine on the 
surface, where its temperature is reduced to about 8° F. below 
zero. The solution of chloride of calcium is pumped through 
the smaller tube to the bottom of the hole, and then rises 
through the larger tube to the surface. In this process, the 
material is frozen first and hardest at the bottom where the 
greatest pressure is. Since this freezing mixture is much 
heavier than water, the pressure inside the pipes is greater than 
that outside, so that there is a tendency to burst the tube con¬ 
veying the freezing solution, thus allowing it to escape into the 
sand outside and rendering it incapable of being frozen. 

34. In the Gobert system, anhydrous ammonia is sent 
down the inner tube (which is then usually made of copper) 
and allowed to vaporize in the tubes, thus freezing the ground 
directly instead of allowing the ammonia to cool a mixture that 
freezes the ground indirectly, as in the Poetsch process. The 
ammonia gas is drawn off by a pump and reliquefied by com¬ 
pression and used over again. As the pressure is less inside 
than outside the tubes, if a leak occurs in the tube any water 
entering will be immediately frozen and the leak thus stopped. 

The .pipes may be driven well outside of the intended shaft 
area and a wall of earth frozen around the shaft, the central 


74 DRIFTS, SLOPES, AND SHAFTS. PART 2 


portion or shaft area being removed before it is frozen. In 
most cases, however, the ground has to be frozen solid and 
then blasted as though it were rock. 


KIND-CHAUDRON AND LIPPMAN SYSTEMS 

35. Kind-Chaudron System.— This system is appli¬ 
cable only to circular shafts, and is adapted to sinking through 
strata with heavy feeders of water that render the work of 
sinking by ordinary methods wholly impracticable. The exca¬ 
vation is carried down to water level by the ordinary methods 
of sinking, and the shaft is lined to this point with timber or 
masonry. Boring is then commenced by means of a large 
trepan, or rock-drilling tool, suspended in the shaft. The 
diameter of the excavation to water level must be sufficient to 
allow for the thickness of the walling, or timbering, so that the 
latter will not interfere with the use of the trepan for sinking 
below this level. The excavation is effected in two or more 
successive operations. The first trepan used cuts a hole in the 
center of the shaft from 4 to 5 feet in diameter; this is called 
the guide pit and is kept at least 35 feet in advance of the 
second cut, which is made by enlarging the guide pit by means 
of a special trepan. During the entire boring, the water is 
allowed to accumulate in the hole, which often stands full, and 
the boring is done underneath the water. 

36. The first trepan, which is shown in Fig. 20, consists 
of a head a made of wrought iron and provided with steel 
teeth b on its under surface. The action of the cutting tool 
is the same as that of a churn drill. The trepan is suspended 
in the shaft by means of heavy iron rods attached to one 
end of a large walking beam at the surface, and the weight 
is partly balanced by a counterpoise at the other end of the 
beam. An engine operates the beam, raising the rod to a 
height varying from 10 to 20 inches and dropping it to the 
bottom. The trepan is turned by men who stand on a platform 
built above the level of the water in the shaft. In making this 
first cut, the hole is cleared by means of a sheet-iron sand 



DRIFTS, SLOPES, AND SHAFTS. PART 2 75 




Section on A-A 


Fig. 20 


pump about 6 feet long, 
which is raised and lowered 
by the trepan rods. 

37. The second cut is 
an enlargement of the first 
and is made with a trepan 
that usually weighs from 
36,000 to 50,000 pounds. 
It is quite similar to the first 
trepan, being formed of a 
wrought-iron bar having 
teeth attached to that por¬ 
tion that extends beyond 
the diameter of the guide 
pit. It is guided by means 
of a cradle, or iron bar, that 
fits closely within the ex¬ 
cavation made by the 
smaller trepan. The teeth 
on the large trepan are so 
set that they cut the bottom 
of the annular portion sur¬ 
rounding the guide-bore pit 
in a conical, sloping surface, 
so as to allow the fragments 
and cuttings to roll into the 
smaller shaft, where they 
are caught in a sheet-iron 
bucket previously lowered 
to the bottom of the guide- 
bore pit. Sometimes it has 
been found advantageous to 
use scrapers, which drag 
around after the trepan and 
sweep the material down 
the incline and into the 
bucket. 
































































76 DRIFTS, SLOPES, AND SHAFTS, PART 2 


The excavation having been made of the required size in 
two or more successive operations, the shaft is lined with 
iron tubbing, which is built in sections 4J to 5 feet high 
and added at the top as the whole is lowered from the 
surface. 

To assist in supporting the great weight of the steel tubbing, 
it is provided with a water-tight bottom in which is a nozzle 
having a stop-cock by which a sufficient amount of water 
can be let into the tubbing to sink it gradually. The tubbing 



is thus lowered in the shaft till it finally rests on the solid 
bed leveled to receive it. A special moss packing below the 
tubbing makes a water-tight joint when the water is pumped 
out. 


38. Lippman System. —The Lippman system dif¬ 
fers from the Kind-Chaudron system in that the shaft is 
bored to the desired diameter at one operation by using 
the cutting tool shown in Fig. 21. The tools are made and 
the cutting teeth are secured in a manner similar to that 
employed in the Kind-Chaudron method. 


SHAFT TIMBERING 


timbering in various kinds op ground 

39. Introductory.— In America, shafts are very gen¬ 
erally lined with timber, hence the terms shaft timbering 
and shaft lining are often used synonymously. Although 
the term shaft timbering will be used in the succeeding 
descriptions, it is to be understood that many of the methods 






DRIFTS, SLOPES, AND SHAFTS, PART 2 77 


referred to apply equally well to masonry, steel, or any other 
form of shaft lining. 

40. Effects of Local Conditions. —The object and 
character of shaft timbering vary with the nature of the 
enclosing strata and with the depth below the surface. Thus, 
the methods used in rock, in loose material, and in watery 
or running strata are very different. In a shallow shaft, 
however, it is not advisable to change the lining to suit 
changes in the strata, and the thickness is made throughout 
so as to meet the requirements at any point of the entire 
depth. 

In hard material, only such timbers are introduced as 
are necessary to furnish support to the guides, pipes, wires, 
etc. that are carried down the shaft. In loose material, 
the object of timbering is to give support also to the sides 
of the excavation. In watery strata, the pressure of the 
water behind the timber is another point that must be con¬ 
sidered. Water encountered in the sinking of a shaft finds 
its way at once to the excavation or follows down behind 
the lining and collects in the bottom of the shaft, unless 
kept out by the shaft lining. If the lining is built tightly 
against the sides of the excavation, so as to impede or stop 
the flow altogether, the water rises behind the lining to the 
water level of the strata, and the lining is subjected to a 
pressure dependent on the head of water. The strength of 
the lining must be sufficient to withstand this pressure. 

41. Water Pressure Against Lining. —In cases 
where a lining has to resist the pressure resulting from a cer¬ 
tain head of water, the following formula may be employed. 
It will determine the thickness of a white-pine lining that 
will possess a sufficiently high factor of safety to resist the 
pressure. 

Let t = thickness of white-pine lining, in inches; 

s = clear unsupported span of timber, in inches; 
d = depth, or head, of water, in feet. 

Then, t = .0\6s\fd 

431—6 


78 DRIFTS, SLOPES, AND SHAFTS, PART 2 


It must be remembered that the water rarely, if ever, heads 
to the surface, hence the head of water supported by the 
curbing does not mean the depth of curbing below the surface. 

Note. —While this formula seemingly applies only to white-pine 
timber, the same formula will give results that are practically correct 
for the other timber used in shaft linings. 

Example— Find the thickness of white-pine curbing required for a 
coffer dam when the depth of the water head is 100 feet, the clear span 
of the end plates of the shaft being 7 feet. 

Solution. —Substituting the given values in the formula, f=.016 
(7X12)\/100= 13.44; hence a 14-in. timber would be used. Ans. 

42. Material of Lining.— Yellow pine was formerly 
thought to be the only wood suitable for shaft lining, but on 

account of its great cost it has been 
largely superseded by hemlock, black 
and white oak, and other woods. An 
ideal plan would be to have the tim¬ 
ber cut of proper length and notched 
or framed before being delivered, but 
this is not often practicable, and, in 
general, the timber is framed on the 
ground by contract at so much per 
set (a set being one horizontal layer 
of timber of whatever size is used). 
If the framing is done by day labor, 
two men are kept busy cutting and 
carrying timber about one-third of 
the time, and are employed on drills or at other labor when 
not framing. 

43. Timbering in Rock. —Where a shaft or a portion 
of a shaft is excavated from hard-rock strata, the only timber¬ 
ing necessary is the cross-timbers, or buntons, to support the 
guides in the hoisting compartments of the shaft and the lines 
of pipes or wires. The buntons b. Fig. 22, are set in hitches h, 
cut in the rock face and firmly wedged in line, one above the 
other, by wedges w, w. At times the hitches are cut square 
and those on one side made deeper to permit the other end of 
the stick to be placed in the hole opposite. 



Fig. 22 



DRIFTS, SLOPES, AND SHAFTS. PART 2 79 


The buntons are spaced from 6 to 8 feet apart, one above 
another, on each end of the shaft, and between the several 
compartments of the shaft. When it is desired to separate the 
compartments of the shaft, as in the case of an airway or man¬ 
way, planks are spiked to the buntons or built between them 
to form the partition. 

44. Timbering in Loose Dry Material. —In good 
ground, shafts have been sunk to a depth of 200 to 300 feet 



Fig. 23 


by using 3"X12" planking set on edge, but beyond this depth 
it is better to use 4-inch or 5-inch planks. When an especially 
soft, wet, or crumbling stratum is met, such as wet sand or 
fireclay, the planking is sometimes laid flatwise. If the sides 
of the shaft are not self-supporting and tend to crumble into 
fragments of varying size; if boulders that are likely to become 
detached are found, or if the strata are jointed and faulty, 
















































80 DRIFTS, SLOPES, AND SHAFTS. PART 2 


then, in order to preserve the shaft and to avoid accident from 
earth or rock falling to the bottom from the side walls, it is 
necessary not only to line the entire excavation with plank, but 
this planking must be supported by heavy timber sets placed 
inside the planking as shown in Fig. 23. 

The timber sets a are spaced equidistantly and are separated 
by the posts b. The lagging c, composed of closely fitting 
planks, may be driven in behind the timber sets, or it may be 
first placed in position and the timber sets or frames added 
afterwards. Cross-buntons d are also inserted in each set to 
separate the compartments. Where a greater strength of tim¬ 
bering is required than is given by the form shown in Fig. 23, 

the sets a may be 
placed one on top of 
the other, i. e., skin to 
skin. 

45. An open crib 
of timbers, similar to 
that shown in Fig. 24, 
may also be employed 
in loose ground, the 
openings between the 
timbers being gradu¬ 
ally filled up com¬ 
pactly by the loose 
material. After the timbers have been placed in position, 
triangular strips, or corner pieces, A are spiked to them in 
each corner of the shaft. This open crib may be built either 
from the top downwards or from the bottom upwards. 

46. Timbering From Bottom Upwards. —Instead 
of building the timbering from the top downwards, it is 
frequently built upwards from the bottom in sections of 10 
to 15 feet, depending on the character of the ground. The bot¬ 
tom of the shaft is carefully leveled with a carpenter’s level 
and straightedge; and, by measurements made from the plumb- 
lines hung from the shaft corners, a set of timbers is placed so 
that the inside is in line with the edge of the sills, or shaft 











DRIFTS, SLOPES, AND SHAFTS. PART 2 81 


templet. After the whole set is accurately leveled and joined, 
wooden wedges are driven between the timbers and earth at 
each corner. The wedges should be long and tapered through¬ 
out, and while one man drives the wedge the other holds the 
set in place with a bar. Great care is taken to get this first 
set level and in line with the shaft templet, as it is the founda¬ 
tion for the other sets. 

47. After this foundation set has been placed in position 
and wedged, another set is placed on it and leveled and wedged 
in like manner. In this manner, the work is continued until 
the templet or next section of timbering is reached. If the 
sinker has measured correctly and has made due allowance 
for the number of sets required to 
close the distance between the shaft 
bottom and templet, his sets will close 
this space exactly. The inside edges 
of the planking are brought flush with 
the inside edges of the templet, and 
iron straps, about 2\ in.XJ in.X15 ft., 
provided with nail holes are hung 
from the surface downwards, con¬ 
necting all the planking and suspend¬ 
ing it from the templet. The straps, 
or hangers, are placed on the sides 
and ends of the shaft at distances of 
2 to 3 feet apart, and they should break joints vertically as 
the timbering proceeds. If a small space is left between the 
last set and the templet and the planking does not close exactly, 
a closing set is necessary. For this purpose, a regular set is 
cut down to the required size by the rip saw or adz. How¬ 
ever, the sinker should make his measurements and calculations 
so that no closing sets are required. 

No cavities should be allowed to remain behind the timbering 
after it is completed, except in ground that swells. If cavities 
are found in the strata, or if more earth has been taken out 
than was necessary, the space must be filled with ashes, 
straw, etc. 




82 DRIFTS, SLOPES, AND SHAFTS. PART 2 

48. Timbering* in Swelling Ground. —A form of tim¬ 
bering often employed in swelling ground is a cribwork of 
heavy timbers, such as is shown in Fig. 25. These timbers 
are notched together after the fashion of a log cabin. One 
side of the timbers may be faced, as shown in the figure, so as 
to form the face of the shaft, but the back of the timbers is 
preferably left round. When the ground swells, the material 
more readily works out between the timbers, and can be 
removed from time to time, as may be found necessary. An 
important feature of the work in dealing with swelling ground 
is to keep the material as dry as possible, since the moisture 
causes the swelling. In such swelling ground, a space at 
least 6 inches wide is sometimes cut out all around the sides 
and ends of the shaft, and filled in loosely with moss, straw, 


Fig. 26 

sand, or ashes, allowance being made for the probable expansion 
of the ground. When the timbering, by bulging, shows signs of 
excessive pressure behind, as shown in Fig. 26 (a), the diffi¬ 
culty may be overcome by carefully removing two or more 
planks from the shaft at this point, and excavating such mate¬ 
rial as may be necessary, all around behind the timbers, as 
shown in ( b ). The manway .thus formed should be carefully 
drained by a pipe conducting the water to the sump or other 
lodgment. This manway should be timbered and cleaned out 
from time to time, as may be necessary; the bulged timbers of 
the shaft should also be replaced by good ones. 

49. Timbering* in Very Wet Ground or Quicksand. 

In wet ground, timbers should be closely joined. At times, it 
is necessary to make a water-tight joint between each set of 






















DRIFTS, SLOPES, AND SHAFTS, PART 2 83 


timbers to keep the water from entering the shaft; for this 
purpose, timbers have been laid in cement, but better results 
are obtained by backing the timbers with cement. A form of 
timbering that always gives good results, introduced for the 
first time in the sinking of the Ladd shaft at Ladd, Illinois, 
is that shown in Fig. 27, which illustrates a section of curbing 
passing through a stratum of quicksand, and through soft 
material overlying the same. At a point above the soft mate¬ 
rial, the 3"X8" curbing plank employed for the shaft lining is 
laid flatwise, as shown at a, increasing the thickness 
of the curbing from 3 to 8 inches. When the quick¬ 
sand is reached, the 8-inch plank is alternated by 
6-inch plank, forming the corrugated backing shown 
at b; the effect of this rough backing is to clog the 
drainage that would otherwise find its way down the 
back of the curbing, and greatly reduces the amount 
of water entering the shaft. 


50. Setting 1 Timber in Quicksand. —The 
chief difficulty in sinking through quicksand is that 
arising from the flow of the soft material into the 
excavation before the timbers can be placed in 
position. To prevent this as far as possible, the 
excavation should be timbered well down to the bot¬ 
tom of the shaft. Fig. 28 is intended to give a gen¬ 
eral idea of the inflow of sand and the method of Fig - 27 
setting the timbers. The lower timbers have been set, jacked 
up, and spiked. Blocks a, used to support the back of the 
lining, are knocked out by the next set of timbers when it is 
driven to its place. It is necessary to provide a temporary 
foundation for the jacks, which in this case is afforded by the 
sills shown. The form of lining employed is the alternate 
narrow and wide plank laid flatwise. To reduce the flow of 
sand temporarily, spiling has been driven between the timbers; 
but the spiles must be removed before they throw too much 
weight on the lining. To support the timber while the jacks 
under the set are being lowered far enough for a new timber 
to be placed over them, cleats are spiked on the timbers as fast 
















84 DRIFTS, SLOPES, AND SHAFTS, PART 2 


as each timber set is laid in place. If the timbers cannot be 
forced into place by hand or driven with a sledge, a jack, 



Fig. 28 

similar to those shown in Fig. 28, is used, being fastened to a 
piece of 6"X6" or 8"X8" timber, about 1 foot shorter than the 
inside dimensions of the shaft. 


51. Timbering’ a Wet Surface and Subsoil.— It fre¬ 
quently happens that much annoyance is caused in an other¬ 
wise good shaft by a large amount of surface water finding 
its way into the shaft through the drift and subsoil overlying 
the hard pan. When this is the case, it will pay to enlarge 
the shaft through the drift and subsoil to the hard pan, and 
line the excavation in the ordinary manner by light timber 



Fig. 29 


frames and sheathing plank behind them. The excavation 
should be carried about 2 feet into the hard pan, in order to 














































DRIFTS, SLOPES, AND SHAFTS. PART 2 


85 


afford an opportunity of making a good water-tight joint, so as 
to prevent the surface water from finding its way into the 
shaft. The heavier permanent shaft lining is then built up 
from the bottom within this enclosure, the space between the 
two linings being filled with clay well rammed as the timbers 
are placed in position. This forms a water-tight shaft lining, 
as shown in Fig. 29. The thickness of the clay should not 
be less than 10 or 12 inches. 


PROVISIONS FOR DRAINAGE OF WATER 

52. Water Rings. —In most shafts a certain amount of 
water collects during the sinking as well as after the shafts 
are completed. Some 
water will usually be 
found flowing over the 
rock or over the lining. 

To draw this water away 
and prevent the annoy¬ 
ance due to its constantly 
running down the shaft, 
a notch may be cut in the 
rock about the shaft as 
shown in Fig. 30, or, if the shaft is timbered, water rings, or 
curb rings, are built in the lining as shown in Fig. 31. These 
catch the water as it runs down the rock or lining and conduct 
it usually to one corner of the shaft, from whence a pipe leads 
to the sump at the bottom or to a lodgment or coffer dam. 

53. Lodgments, or Basins.— Openings varying in 
height from 6 to 8 feet and of a width equal to that of the 
shaft are sometimes driven from the end of the shaft. These 
openings, known as lodgments , or basins , extend from 50 to 
60 feet back from the shaft and are intended to serve as 
receptacles for large quantities of water collecting during sink¬ 
ing operations. They are, as a rule, constructed on rock or 
other hard ledges through which the shaft passes. The hard 
stratum is smoothed and a floor made of heavy timber or 



Fig. 30 





86 DRIFTS, SLOPES, AND SHAFTS, PART 2 


brick laid in cement; the sides are treated in the same way, and 
the chamber thus made is arched over; across the mouth, some 
8 or 10 feet from the shaft lining, a dam of timber or brick 
laid in cement is built, as shown at Fig. 32 (a). 


54. Instead of damming in the manner shown in Fig. 32 
( a ), the water may be caught in a basin, as shown at ( b ). 
An opening large enough to admit a man’s body is left in the 
dam so that the lodgment can be periodically examined. In 
the opening a pump is erected, as shown in the illustration, and 



the water pumped to the surface, the power for the pump being 
supplied from the surface. As much of the water in a shaft 
usually comes from within a comparatively short distance of 
the surface, the use of such lodgments saves pumping from the 
shaft bottom. 


55. Sump. —As shown in Fig. 33, the shaft excavation is 
always carried far enough below the cage landing at the shaft 
bottom to provide a catch basin, or sump, large enough to 
hold the water draining into it from the shaft and from the 






























































































DRIFTS, SLOPES, AND SHAFTS, PART 2 87 


workings during 24 hours. The depth of the sump will be 
limited by the suction of the pump, or the depth from which the 
pump will draw water. If the area of the shaft is not sufficient 
to afford the required capacity, the sump must either be 
extended at one end or a second sump provided. 

56. Framing* Above Sump.— When the bottom of the 
shaft is reached and the sump has been made by carrying the 
excavation several feet below the floor of the seam, a heavy 



Fig. 33 


substantial frame must be built for the support of the shaft 
timbers. The cage landing is first made by placing two heavy 
square timbers a, Fig. 33, under each hoistway. These timbers 
should be 10 in.X12 in. or 12 in.X16 in., according to the 
size and weight of the cage, and should occupy a position about 
under the rails on the cage. They are well bedded in the 
strata on each side of the shaft, and set low enough to make 
the floor of the cage, when the latter is resting on the timbers, 
level with the floor of the landing. When this has been done 




































88 DRIFTS, SLOPES, AND SHAFTS. PART 2 

in each hoistway, heavy longitudinal sills b are laid over them, 
one on each side of the shaft; cross-timbers c are boxed into 



Fig. 34 


the sills to keep them the right distance apart and to form a 
solid frame for the cage landing. Substantial posts d are then 
set at the corner of each compartment. Heavy caps, or col- 

































DRIFTS, SLOPES, AND SHAFTS. PART 2 89 


lars e are framed to rest on these posts, and cross-timbers / are 
boxed into these caps above. The whole frame is brought to 
such a height as will correspond to the height of the heading, 
and the shaft timbers, or lining, g are made to rest on the top 
of this frame. 

Underneath the cage timbers a heavy planks, not shown in 
the illustration, are inserted so as to cover the sump to pre¬ 
vent material from falling in and avoid the necessity of fre¬ 
quent cleaning. Without a cover, there is also the danger of 
animals falling into the sump and being drowned before they 
can be got out. This cover should be so arranged that it may 
be easily and quickly removed at any time. 

57. Coffer Dam. —A coffer dam is a section of solid 
lining designed to dam back the water coming from a stratum 
of water-bearing rock encountered in the sinking of a shaft. 
An example of a coffer dam is shown at k, Fig. 34. At any 
point where a water-bearing stratum of rock is encountered, 
sufficient material is excavated from the watery strata to allow 
a good cement backing to be inserted behind the shaft timbers; 
this excavation should be carried a short distance into the 
underlying and overlying strata so as to form a water-tight 
joint with each stratum. The space thus excavated is filled 
with concrete either at the same time that the timbers are 
put in place or later from an opening left in them. The timber¬ 
ing is also often made much stronger and heavier at this 
point. The operation of damming back the water is known 
as coffering. 


EXAMPLES OF SHAFT TIMBERING 

58. Three-Compartment Shaft. —Fig. 34 shows the 
general form of construction of a three-compartment shaft, 
the details of which have already been described. In the illus¬ 
tration the two near sides of the hard-pan walls are broken 
away; some portions of the sheathing are shown removed, and 
also the near portions of the concrete walling d. This walling 
is erected through the surface drift and subsoil into the hard 
pan, so as to form a water-tight joint at this point. The exca- 



90 DRIFTS, SLOPES, AND SHAFTS. PART 2 


vation was first lined in the ordinary way with timber frames 
and light board sheeting c, and the concrete d built up between 
this and the lining ^ of the shaft. At a, a water-bearing 
stratum of rock was encountered and shut off by the coffer 
dam k and the concrete filling /. Below this point the ordinary 
shaft timbering was continued. 

59. Shaft Sunk Through Quicksand. —The sinking 
of a water shaft at Gilberton, Pennsylvania, furnishes a good 
example of the heavy timbers required when sinking through 



quicksand. It was estimated, in this case, that 6,000,000 gallons 
of water must be handled daily. This required a shaft mea¬ 
suring 22 ft.X26 ft. 8 in., out to out of timbers. For the 
first 87 feet below the surface, the shaft passed through a 
peculiar formation composed of sand, clay, gravel, shale, and 
boulders, and containing so much water that it resembled quick¬ 
sand. Fig. 35 is a plan of the timbering near the surface and 
Fig. 36 an elevation of the timbers, from the surface to the 
rock. As shown in Fig. 35 and in the upper part of Fig. 36, 
the timbering consisted of 20-inch round timbers a with 6-inch 
lagging b on the outside; 4-inch planking c was spiked to the 

















































DRIFTS, SLOPES, AND SHAFTS, PART 2 91 



inside face of the round timbers a, and 12-inch square-timber 
frames d placed inside of these. Horn sets, or bearing tim¬ 
bers, e, 28 to 30 feet 
long, were introduced 
at intervals of 7 feet, 
center to center, 
making a total of 
twelve sets of these 
timbers. After the 
shaft reached rock, at 
a depth of 87 feet, 
only the inner lining 
was used. Several 
streams of water were 
tapped during the 
sinking, and coffer 
dams were built in the 
shaft at these points; 
the first was at a 
depth of 157 feet; the 
second, 250 feet; the 
third, 379 feet; and 
the fourth, 482 feet. 

All of these, except 
the last, were tem¬ 
porary, being main¬ 
tained during the 
sinking only. The 
last, or permanent, 
dam consisted of ten 
sets of 12"X 12" tim¬ 
ber placed skin to 
skin, the last set rest¬ 
ing on the rock, which 
was dressed to a level 
bearing or seat, and 
1 foot of oakum placed about the bottom of the ring, while the 
back of the timbers was lined with clay. 




































































































92 DRIFTS, SLOPES, AND SHAFTS, PART 2 

60. Timber Joints.— Several of the most simple forms 
of timber joints in common use are shown in Fig. 37. Each 
one of these has special advantages that make it more or less 
suitable for different conditions. At (a) is shown a simple 
square butt joint that requires no framing, but simply the 
cutting of the timbers to the exact length. The butt joints 
are made to alternate, as shown. By reason of its cheapness 


and simplicity, this form is adapted to shallow shafts where 
the lining is from 2 to 4 inches thick. The triangular corner 
piece is spiked in place after the timbers have been inserted 
and wedged. 


61. At Fig. 37 (b) is shown a simple half-and-half box 
joint made of timbers and capable of resisting heavy side pres¬ 
sure. The joint shown at (c) is used when the timbers must 
be sprung into place, as in certain soft strata that are not self- 




































DRIFTS, SLOPES, AND SHAFTS, PART 2 93 


supporting; also, in places where the space for the lining is 
limited. The joints in adjoining sets are generally made to 
alternate as in the joint at (a) ; but in some cases this is not 
done. This arrangement is illustrated in the view at (d), where 
the timber at the left is supposed to represent a side timber 
and the other an end timber. The recesses in the side timbers 
are all in line, vertically, but do not match with the correspond¬ 
ing end timbers. On the contrary, the latter break joints, 
horizontally, being dropped one-fourth, one-third, or one-half 
its width, as at (d), below the corresponding side timber. 

G2. A box-and-tenon joint is shown at (<?), Fig. 37. It is 
more expensive to make, but it is capable of resisting a great 
side pressure; in this 
case both the side 
and end timbers 
alternate so as to 
break joints. These 
timbers cannot be 
sprung into place, but 
must be built up. 

The joint shown at 
(/) is similar to that 
at (c) except that the timbers are boxed half and half, making 
the end timbers level with the side timbers of the shaft. 

63. The form of framing shown at Fig. 37 ( g ) is princi¬ 
pally used in the portions of shafts that pass through quick¬ 
sand, where the lining must be kept close to the bottom of the 
shaft. 

An expensive but very efficient joint capable of resisting a 
great side and end pressure is shown at (/*), where one view 
shows the complete joint and the other the timbers moved apart 
so as to show more clearly the construction of the joint. At (i) 
is shown what are called horn sets, or hearing timbers. These 
consist of a modification of the joint shown at (a), longer 
timbers being inserted at regular intervals in the lining. Gener¬ 
ally, the long timbers in each of two adjoining sets are extended 
so as to project from 18 inches to 2 feet into the strata, giving 



431—7 












94 DRIFTS, SLOPES, AND SHAFTS, PART 2 


a substantial support to the lining. The distance between these 
horn sets depends on the character of the strata. Examples of 
horn sets are found at e , Fig. 36. 



Fig. 39 

04. Fig. 38 shows a method of setting the buntons B into 
the wall plates, or timbers, A. The ends of the buntons rest in 
grooves cut ^ inch deep in the wall plates, with which they 
break joints in a horizontal direction. 

05. Square-set timbering is adapted to large shafts or 
where the timbers have to resist heavy pressures. This form 



of timbering is wasteful in the use of timber on account of 
both the size and the quantity of the timber required. The 



























































































DRIFTS, SLOPES, AND SHAFTS. PART 2 95 


form of the joint is simple, as the timbers are in general, 
slightly boxed into one another. Fig. 39 shows the general 
construction in the timbering of a three-compartment shaft 
by means of square sets. Some of the timbers are omitted or 
partly broken away for the purpose of showing the form of 
joint employed. A are the side plates, B the end plates, C 
cross-buntons, and D posts, punch blocks, or studdles. 

66. The joints may be given any of the forms shown in 
Fig. 40. If the joint shown at ( b) is employed, the cross- 
bunton shown at (a) must be put in place from below. The 
advantage of this is that, if the timbering must be kept close 
to the bottom while sinking, 
the bunton going in from be¬ 
low can be left out at first, so 
as to allow more room for 
the workmen. 

If the side plate is re¬ 
cessed as at (c), the bun- 
ton must be put in from 
above. In either case the 
post shown at ( d ) is placed 
in the recess provided for 
it on top of the plates 
shown at ( b ) and (c). 

Fig. 41 shows another method of joining end and wall plates, 
the post F being boxed into the plates at its top as well as at its 
bottom. In this example, a 2-inch strip N is nailed to the plates 
on which the lagging is to rest. 

67. Numerous other forms of joints are used in square-set 
timbering, but these will serve to illustrate the aim one should 
always keep in view, namely, that a timber should not be unnec¬ 
essarily weakened by cutting away more than is absolutely 
required in making the joint. 

In framing the timbers, regard must always be had to the 
manner in which they are put together in the shaft. When the 
timbering is done from the top downwards the sets are kept in 
position, while being lowered, by means of hanger bolts made 

























96 DRIFTS, SLOPES, AND SHAFTS, PART 2 


of round-iron rods, bent into a hook at one end and provided 
with a thread and a nut at the other end. By arranging the 

bolts as shown in Fig. 42, 
the various buntons and 
frame pieces will be held 
securely between the end 
and the cross pieces. 


CURBS 

68. Def i nitions. 
Applied to coal mining 
the term curb means a 
support, or foundation 
for the lining of a shaft, 
and is a term commonly 
used in England in con¬ 
nection with circular 
shafts lined with ma¬ 
sonry. The heavy 
frame, or sill, at the top 
of the shaft is also some¬ 
times called the curb, 
since in some cases the entire shaft lining is hung from it. 

The term curbing is also variously used in different countries 
and in different sections of the same country, giving rise to 
much confusion in describing shaft-sinking operations. Thus, 
in England, this term commonly means the lining that is placed 
on top of the curb, or shelf, made in the rock as a foundation 
for the shaft lining. In different parts of America, on the other 
hand, the terms shaft curbing, shaft cribbing, and shaft lining 
are used synonymously. 

69. Wedging Curbs.— When the solid rock is reached in 
sinking, the length and the width of the excavation is slightly 
increased and the top of the rock is carefully leveled off, so as 
to form a shelf, or curb, on which to rest the lining above. 
This shelf should not be blasted out, as this will shatter the 
under rock and make it impossible to make a tight joint between 





































DRIFTS, SLOPES, AND SHAFTS, PART 2 97 


the rock and the shaft lining. A wedging curb a, Fig. 43, made 
of iron or wood is laid on this shelf, a tight joint between the 
curb and the rock sometimes being made by means of a layer 
of cement under the curb and by ramming cement or concrete 
back of the timbers. If it is not desired to make a water-tight 
joint between the lining and the rock, a water ring similar to 
that shown in Fig. 31 is made in the wedging curb. Wedges b. 
Fig. 43, are placed between the curb and the rock, and on top of 



the curb the tubbing c is laid. The tubbing is tightened by 
means of the wedges d, which are backed by the concrete e. 

If a rectangular shaft is to be lined with timber, the wedging 
curb usually consists of a horn set made of heavy timbers cut 
longer than the length of the shaft and laid into excavations 
made in the surrounding strata and on a cement base. 

Fig. 44 shows a more elaborate joint between loose ground 
and solid rock. The timbers a , b, c, d forming the lower 





























































98 DRIFTS, SLOPES, AND SHAFTS. PART 2 


portion of the sinking shoe are left in place and the shaft 
lining e is built up inside of them. A puddling k of clay or 
cement is forced under the bottom of the shoe or caisson to 
keep back the running material or quicksand /. Next a grout li 
of cement and gravel is built against this clay and around 
the point of the shoe. The space g between the inside lining of 
the shaft and the grout h is filled in with Portland cement. 

70. Supporting: Curb. —It is sometimes necessary to 
employ what is called a supporting: curb. This consists 
of a strong wooden or cast-iron curb supported on horizontal 
bars located in holes drilled in the strata and projecting into 
the shaft. These bars are in a horizontal plane and furnish 
the required support for the curb laid on them. The masonry 
that is to form the shaft lining rests on this curb. This 
arrangement is generally temporary, and is used when the shaft 
lining is built in sections. 

TIMBER, 31ASONRY, AND METALLIC LININGS 

71. Masonry Shaft Lining*. —A lining that consists of 
brick, rock, or concrete is known as a masonry shaft lining, 

and is used where tim¬ 
ber is scarce or where 
the character of the 
strata is such as to 
render timber lining 
impracticable. Some¬ 
times only a section of 
a shaft is lined with 
masonry. These 
linings are usually laid 
on a wedging curb and 
are carried upwards in 
sections, as shown in 
Fig - 45 Fig. 45. Each section 

is laid on a ring a of cast iron or timber resting on a temporary 
shelf or seat b cut in the rock. As the lower sections are built 
up, the shelf b supporting the masonry above is cut away in 













drifts, slopes, and SHAFTS. PART 2 9 


places and the masonry below carried up to furnish the neces¬ 
sary support for the upper section. In this manner, all the 
shelf is finally cut away and replaced by the masonry of the 
lower section. 


72. Metallic Lining*, or Tubbing*. —The term tubbing 
is an English term applied to the metal, and sometimes to the 
timber, lining of a circular 
shaft, and is particularly 
used when such linings 
are employed to keep 
water from flowing into a 
shaft. The three kinds 
of metal tubbing are: 

(1) That which is made 
in sections with outside 
flanges and is simply 
wedged firmly into place 
by wedges placed between 
the tubbing and the wall 
of the shaft; (2) that 
which is made in sections 
and bolted together on the 
inside both at the vertical 
and horizontal joints; 

(3) that which is made up 
of complete rings of 
cylinders bolted together 
by means of horizontal 
flanges. 

The metal tubbing. 

Fig. 46 (a), consists of 
cast-iron segments vary¬ 
ing' - from 18 to 36 inches 


according to the pres¬ 
sure to be resisted. The 
segments are flanged at top, 
pieces of pine are put 



Fig. 46 


bottom, and 
between them 


as 


ends and -|-inch 
they are put in 

















































































100 DRIFTS, SLOPES, AND SHAFTS, PART 2 

place, thus making tight joints both horizontally and vertically. 
To prevent breaking the metal lining by the pressure of air 
or gas behind it, the metal is perforated ; these holes are loosely 
plugged, so that any particular pressure coming on them will 
force out the plugs. Fig. 46» ( b ) shows a method of walling 
a circular shaft with brick, the brick being laid on a cast-iron 
wedge curb s. 

73. Wood Tubbing-. —Wood tubbing may be of two 
kinds: (1) Planks, 2 or 3 inches thick, placed vertically and 
having beveled edges like barrel staves; (2) thick blocks simi¬ 
larly beveled and placed vertically. Fig. 46 (c) shows an 
example of plank tubbing. The planks have timber curves m 
placed inside them and spiked to them. The curves are kept 
apart by punch blocks n and are tied together and fastened to 
the shaft sills l by the stringers r. The sections of the shaft 
( b ) and ( c ) are shown supported on a rock bench while the 
metal tubbing is being put in place below. When a shaft has 
been lined up to the rock bench, this is cut away and the metal 
tubbing joined to the other portion of the shaft lining by small 
metal sections called closers. 

74. Calculating Thickness of Metal and Masonry 
Linings. —The following formula is proposed by Mr. W. 
Galloway for calculating the necessary thickness of a cast-iron 
tubbing, or of cement or brick lining: 

wh d 

( r+ivh ) 

in which t = thickness of lining, in inches; 

d = internal diameter of shaft, in inches; 
h= head of water, in inches; 

62.5 

w— weight of cubic inch of water =“j^ 28 = .0361 lb.; 

r=33J per cent, (one-third) of crushing load per 
square inch of material used. 

The crushing strength of the material used should be deter¬ 
mined in each case by experiment, but the following may be 
used as a fair average value: 




DRIFTS, SLOPES, AND SHAFTS, PART 2 101 


Pounds Per 
Square Inch 


Crushing strength of cast ironj. 80,000 

Crushing strength of brick laid in lime mortar. . 1,000 

Crushing strength of brick laid in cement and 

lime. 1,500 

Crushing strength of brick laid in best cement 

mortar . 2,000 

Crushing strength of concrete made from Port¬ 
land cement and 1 month old. 1,000 

Crushing strength of concrete made from Rosen- 

dale cement and 1 month old. 500 

Crushing strength of concrete made from Port¬ 
land cement and 1 year old. 2,000 

Crushing strength of concrete made from Rosen- 

dale cement and 1 year old. 1,000 


Example.— What should be the thickness of tubbing for a shaft 
13 feet in diameter at a depth of 800 feet: (a) for cast iron? ( b ) for 
brick, assuming a mean crushing strength of 1,500 pounds per square 
inch? ( c) for concrete made from Portland cement and one month old? 


Solution. 

.0361X800X12X13X12 

27,031 

k a ) t | 

2 I 

j"80,000 + ^ 0361x800x 12 ) 

.0361X800X12X13X12 

”26,666+347” lm * Ans ‘ 

27,031 

(b) t | 

2 ! 

.0361X800X12) J 
.0361X800X12X13X12 

500+347 31.9, say 32 in. 

Ans. 

27,031 

(O t— \ 

=i 

r bO°o + (Q36 2 x 800 x 12 ) J 

~333£+347” 39 - 7 ’ say 40 in - 

Ans. 


75. Metallic Lining: Supported From the Surface. 

When, on account of the presence of water in the shaft, it is 
necessary to build up the entire lining by adding successive 
sections at the surface, the method illustrated in Fig. 47 is 
used. A tight joint between the lining and the underlying rock 
is made by means of a moss box; this consists of two rings of 
lining a, b, each of which has a flange turned outwards at the 
bottom and inwards at the top. The ring b slides over the 
ring a and the annular space between the ring a and the rock is 













102 DRIFTS, SLOPES, AND SHAFTS, PART 2 


filled with moss c. When the lower section a reaches the 
rock, the weight of the overlying sections forces the section b 
down on the moss, compressing it between the two flanges d 
and e and thus forming a water-tight joint. The sections 
of the tubbing above the moss box are bolted together by means 
of flanges that turn inwards, while a tight joint between the 

flanges is made by means 
of a thin strip of lead. The 
weight of such a lining is 
enormous and in order to 
successfully lower it, a 
diaphragm f is fastened to 
the flange of one of the 
segments just above the 
moss box. In the center of 
this diaphragm is a tube g ; 
as the lining is being low¬ 
ered the weight of the 



that the tubbing meets in 
sinking through the water 
are so great that the weight 
of the tubbing is largely 


counterbalanced. After the 
metal lining is in place, the 
space between it and the rock is usually filled in with concrete; 
as soon as this is set the water can be pumped from the inside 
lining. 


Fig. 47 


76. Steel Shaft Lining.— The use of metal for lining 
shafts has, until recently, been restricted to circular shafts, 
in which iron tubbing was employed. Steel has now been 
introduced and used successfully in the lining of rectangular 
shafts. The method adopted at Ely, Minnesota, by the Oliver 
Iron Mining Company, and shown in plan and elevation in 








































30/6. TRcri/ s 



GO 


6u °l, ir/'oy q/9/ 

// & 


c 


$C 

a 


Nfcj 


"t<\) 


GO 


GO 




CO 


*0 




■jseyfo iff6ua-j 


103 


Fig. 48 





































































































































104 DRIFTS, SLOPES, AND SHAFTS. PART 2 


Fig. 48, has been to use rectangular frames, or sets, after the 
manner of timber frames. These are placed at suitable inter¬ 
vals, with studdles s be¬ 
tween to serve as posts or 
uprights. These frames 
have been lagged most 
successfully with corru¬ 
gated steel. Flat plates 
stiffened by angles could 
be used, but for equal 
strength are more ex¬ 
pensive. There is no 
framing of the sets, as in 
the use of timber, but the parts are put together, after the 
manner of ironwork, by riveted angle bars. Steel rails weigh¬ 
ing from 25 to 30 pounds per yard are used for the wall plates a 
and end plates b, while 3-inch 7J-pound I beams are employed 
as center girts c to divide the shaft into compartments. The 
members of the set are connected together by angle pieces, or 
knees, d , 3J in.X3J in.XJ in., and inches long, each angle 
being secured by two J-inch rivets in each leg. The studdles ,y 
are pieces of 16-pound rail 4 feet long, 
the ends being slotted, as shown in the 
separate view at the right, to receive 
the flanges of the wall plates. 

77. Fig. 49 shows in a perspective 
view a detail of the connection between 
a wall plate a, a center girt c, and a 
studdle s at one side of the shaft lining, 

Fig. 48. The wall plates a are con¬ 
nected to the end plates b, and studs s in 
a similar manner by angle pieces d , as 
shown. The studdles s are not riveted, 
but held firmly in position by the slot in 
each end, in which rest the flanges of the wall plates, while the 
head of the rail rests on the web of the end plate between the 
head and flange of that rail. In this position, the studdle is 


H 


4 

4 


(«) (&) 


Fig. 50 





















DRIFTS, SLOPES, AND SHAFTS, PART 2 105 


held firmly and prevented from moving in any direction. No 
lagging is used, except where the strata require the support of 
the lining. For lagging, old wire ropes interlaced with wooden 
lath have been used; but with the purpose in view of retarding 
the spread of fire, 
metal lath or corru¬ 
gated steel plates may 
be used. 

78. In sinking, 
the steel sets, shown 
in Fig. 48, are sus¬ 
pended by hangers in 
the same manner as are timber sets. These hangers, Fig. 50, 
consist of simple bar iron having at each end a hook that 
passes over the flanges of the wall plates, a wedge being used, 
as shown, to force the hanger from the position occupied i:i 
view (a) into that shown at ( b ). 

In a deep shaft, the weight of the steel lining is taken up at 
intervals by horizontal bearers, or bearing pieces, made of 
30-pound rails set in hitches cut in the rock. The ends of the 
rail extending into the hitches rest in cast-iron chairs, Fig. 51. 
Small steel wedges are driven into the slots a, b, c, and d to 
hold the chair in position on the rail. 

In order to give a firm footing to the steel set resting on the 
bearers, cast-iron chairs of the form shown in Fig. 52 are 

used. These are slipped on the rails 
composing the side plates before the 
latter are placed in position; and 
when these chairs have been ad¬ 
justed in their proper position, small 
steel wedges are driven in the slots 
g, h, i, k. 

79. Concrete Lining’ With. 
Expanded Metal. —The use of 
concrete as a shaft lining is rapidly 
gaining favor. This method has also been successfully used in 
relining shafts. The following are the details of the process 





















106 DRIFTS, SLOPES, AND SHAFTS, PART 2 


used by the Lackawanna Company in relining a shaft near 
Scranton, Pa.: Concrete in the proportion of one part of 
cement, two parts of sand, and five parts of broken stone was 
used; the broken stone is replaced at some places by fine ashes 
obtained from the boiler ash-pit, from which the large cinders 
are removed, or by slate or bony coal. These proportions were 
varied to suit conditions, the concrete being made strongest at 



points of greatest pressure. The thickness of the lining varies 
from 8 inches to 2J feet, and as the shafts that were relined had 
originally been lined with an outer and inner lining, with a 
puddled space between, the inner lining and the puddled mate¬ 
rial were removed and replaced by the concrete, the outer lining 
serving to hold back the walls as the work of laying the con¬ 
crete progressed. A box made of 1J"X8" timber, well braced, 
as shown in Fig. 53, fitting closely against the inner lining and 




















DRIFTS, SLOPES, AND SHAFTS, PART 2 107 


of the same size as the shaft compartment, was used as a form 
around which the concrete was placed. The work was begun on 



Fig. 54 

the rock at the shaft bottom, and carried upwards to the surface 
of the ground. The sheets of expanded metal were T 3 g inch thick 
and 6 ft.X8 ft. in size and overlapped at each meeting point. 
They were placed along the 
sides and ends and at the cor¬ 
ners as indicated in Fig. 54 by 
the broken lines. The shaft 
buntons were taken out and re¬ 
placed by concrete, the concrete 
partition being continuous from 
bottom to top of shaft, except 
for oval openings left to per¬ 
mit examination of the guides, 
as shown in Fig. 55. These 
concrete partitions, as well as 
the concrete lining, are stayed 
by rods h and i set in the con¬ 
crete, as shown by the dotted 
lines in Fig. 55. Bolts were set into the concrete partition to 
serve as fastenings for the cage guides. 



Fig. 55 

















































108 DRIFTS, SLOPES, AND SHAFTS, PART 2 


SPECIAL SHAFT WORK 

80. Retimbering- a Shaft. —As a rule, the shaft lining- 
should last until the shaft is abandoned. It frequently happens, 
however, that, owing to poor timber or bad ground, a shaft 
will need to be relined in places, or it may be desirable to 
replace the entire lining of an old shaft. 

In the retimbering of a shaft, the timbers are removed only 
as new ones are put in their place. If the entire shaft is to 
be retimbered, the work is best performed from the bottom 
upwards. Starting at the bottom, the old timbers are with¬ 
drawn two or three sets at a time, according to the character 
and condition of the strata, and solid substantial frames put in 
their places. It will often be necessary to support the curbing 
above by temporary blocks or posts set under the old frames 
and standing on the new ones. The position of these blocks 
can readily be changed as the new timbers are inserted. Care 
must be taken in this work to tamp good material behind the 
timbers as the latter are built up, so as to leave no cavities 
between the lining and the strata. The same provision must 
be made for the drainage of wet strata, as mentioned in refer¬ 
ence to sinking. A scaffolding is carried up the shaft for the 
workmen to stand on as the work advances. Support for the 
scaffolding may be found in the center buntons and cleats 
spiked to the shaft lining below, or the platform may be hung 
from the advancing work. 

81. Enlarging Shafts. —Though a shaft should always 
be sunk sufficiently large to meet every requirement, it often 
happens, in the later development of a mine, that the output 
cannot be maintained on account of the increased length of 
haul without increasing the size of the mine car, which gener¬ 
ally requires, also, the enlargement of the shaft. The term 
widening is generally applied to any increase in the sectional 
area of a shaft by increasing the length or the width of the 
shaft, or both. As a rule, hoisting ceases during widening, 
but the shaft may be widened at night without interfering with 
day hoisting by using an auxiliary sinking cage. 


DRIFTS, SLOPES, AND SHAFTS, PART 2 109 


The plan ordinarily followed is to widen on one side or one 
end, as by this means timbering already in place is made use 
of, the alinement of the shaft is maintained, excavating is 
done easily, and less readjustment of hoisting sheaves, stops, 
etc. is necessary. 

Fig. 56 represents the top of a shaft that is to be enlarged 
by increasing its length. The manway m is to remain 
unchanged, the end wall opposite to the manway being moved 
out from b to c. The end plates e are to be used again. The 
center partition j dividing the hoistways /, / is to be moved 
from g to h, the distance g li being one-half the distance b c, so 
as to make the hoisting compartments the same size. It is 



Fig. 56 


not customary to make the partition between the hoistways 
solid, but simply to use occasional cross-buntons, excepting 
where there is great pressure on the side timbers. Each 
alternate wall plate is cut at h, so that its end will rest against 
the center bunton h, and a new piece i, reaching from h to c, is 
substituted for the part cut out. The old center buntons j are 
sawed close to the wall plates and may be used again for short 
lengths at /, the buntons h being new timbers. The alternate 
wall plates k, remaining in position, are cut square on the line 
b; the short fillers l butt against these and are framed into the 
wall plates at c ; w is a temporary working platform resting on 
the old end plates and center buntons and passing underneath 
the new center buntons. The material is excavated from the 


431—8 











































110 DRIFTS, SLOPES, AND SHAFTS, PART 2 


space o as the end plates e ' are removed. This material is 
hoisted to the surface by a temporary block and hoisting engine, 
or by the permanent hoisting engine. 


82. A slightly different method of carrying on the work is 
shown in Fig. 57, which represents a plan and a sectional 

elevation of the shaft. 
Cleats a are nailed on 
the old lining and bun- 
tons b placed on them 
across the shaft; on 
these is built a platform 
on which the men work. 
The enlarging is begun 
at the surface and car¬ 
ried downwards, a sec¬ 
tion usually about 8 
feet high being taken 
out from each platform. 
The drillers work on 
the bench c d and load 
the waste directly into 
cars on the cage. The 
end e f is timbered and 
backed as in sinking a 
new shaft. The sides 
e h and / g are tim¬ 
bered as shown. The 
timber joints at the 
corners g and h are left 
undisturbed, but new 
timbers must be used 
for the side timbers, 
except that for each al¬ 
ternate timber the old 
timber is used, in part, a short length of new timber being 
joined to it by a feather-edge joint, so as to bring the length of 
the joined timbers up to that of the new side timbers. When 



Fig. 57 











































































DRIFTS, SLOPES, AND SHAFTS, PART 2 111 


both the length and breadth of the shaft are to be increased, 
an entirely new shaft lining will be required; the excavation in 
this case may preferably be made on all sides of the shaft 
instead of on two sides only. 

In some cases, shafts have been enlarged and retimbered 
very successfully by filling the shaft to the surface with cinders 
and ashes, using such a platform as is shown in Fig. 57 for a 
foundation for the filling. Then commencing at the surface 
the old timbering is 

V//////J/SS///ML vy/////////<//''/// '/as, /'///. '//< 


taken out, the shaft 
enlarged, if desired, 
and new timber put in 
place as if it were a 
new shaft. This is a 
costly procedure, but 
is often cheaper ul¬ 
timately than endeav¬ 
oring to use one or 
more sides or ends of 
the old shaft. 

83. Deepening 
Shafts.— There are 
several methods of 
deepening- shafts 
when it is desired to 
extend them to a 
lower level than the 


Fig. 58 

one being worked. The following three are those most com¬ 
monly used: 

1. First Method .—A false bottom of heavy timbers is 
provided in the sump as a resting place for the cage, and sink¬ 
ing is begun on the bottom of the sump. When the new seam 
is reached, a new sump is made, new guides are extended 
from the bottom upwards to meet the old guides, the false 
bottom is removed, and the cage ropes spliced, or new ones of 
sufficient length are substituted for the old ropes to allow the 
cages to hoist from the lower seam. This method is used often 





















112 DRIFTS, SLOPES, AND SHAFTS, PART 2 


where material is being hoisted during the day and sinking 
done at night. A small sinking cage is slung under the regular 
cage or a bucket is used instead, the material being hoisted to 
the old shaft-bottom level and there taken back into the old 
workings and gobbed. The disadvantages of this method are 
that all the water from the old sump drains through the false 
bottom and down on the sinkers at their work, and there is 

always danger of 
materials falling down 
the shaft on the 
sinkers. 

2. Second Method. 
At a short distance 
from the shaft bot¬ 
tom and on a passage¬ 
way that is not much 
used, a steep slope a h, 
Fig. 58, or small shaft 
is sunk, the depth of 
sinking depending on 
the amount of rock 
necessary to be left as 
a support under the 
old sump while the 
deepening proceeds. 
At the foot of the 
slope a level heading 
h c is first driven to a point directly below the left-hand 
face of the shaft; the roof of this heading is strongly 
timbered by setting the collars in hitches cut in the sides, 
before the work of excavating the shaft below is commenced. 
When this is done, the excavation is begun and carried 
down in exact line with the shaft above, the material being 
removed by a hoisting bucket, operated by a windlass or 
temporary hoisting engine located at some point near the head 
of the slope. The further operation of sinking, timbering, 
etc. is the same as that previously described. When the sinking 
is complete and the shaft timbered, the main sump ^ is drained 



Fig. 59 




















DRIFTS, SLOPES, AND SHAFTS. PART 2 113 


and the two shafts connected by driving upwards from below 
from a strong temporary staging erected at c or downwards 
from the bottom of the sump. 

3. Third Method. —Fig. 59 shows the method of deepening 
a shaft while the upper part is in use, by opening only that 
portion of the shaft area not under the hoistway for a depth of 
12 to 15 feet, and then widening it out the entire size of the 
main shaft. This leaves a roof of rock ( pentice ) that shields 
the men. When another lift has been sunk, the pentice is cut 
away and another started for the next drop. The hoisting is 
done by an underground engine or by bucket and windlass. 

84. Upraising'.— It is often necessary, in order to gain 
time, to drive a shaft upwards from the inside workings as well 
as downwards from the surface. At times, shafts are driven 
entirely from below, this being often the case with escape 
shafts or air-shafts, which are frequently started from the 
workings below. Upraising, or driving upwards, is more 
expensive than sinking, so far as the labor of driving is con¬ 
cerned ; but there is a saving when the work is wholly per¬ 
formed by upraising, as it is then not necessary to set up a 
sinking plant on the surface, and an engineer’s wages are also 
saved. The material is generally stowed in the old workings 
below, but sometimes when room is not available it is sent 
to the surface. Before commencing to drive upwards, a care¬ 
ful survey is made to establish the four corners of the shaft 
in the mine immediately under the surface location. Four 
iron pins are driven in the bottom to mark these corners. If 
necessary, posts or timber cribs are set to secure the roof 
around the place before blasting is begun. 

85. When the excavation has proceeded upwards 8 or 10 
feet in the roof, the bottom is cleaned up, the pins located, and 
the shaft tested for alinement by hanging plumb-bobs in each of 
the four corners. Timbering is then begun by first setting a 
heavy square frame /, Fig. 60, in the roof, resting on substan¬ 
tial posts and sills, as shown in the figure. The inside measure¬ 
ment of the frame must correspond to the size of the shaft in 
the clear when timbered. This frame is exactly located by 


114 DRIFTS, SLOPES, AND SHAFTS, PART 2 


means of the plumb-bobs hanging over the four points pre¬ 
viously established, and is then firmly wedged in place. The 
timbering of the shaft is built up on this frame after the ordi¬ 
nary manner of shaft timbering. The timbering is carried as 
close to the roof as practicable, and a partition is carried up 
dividing the shaft into two compartments. This partition may 
later be used in the operation of the shaft as one of the perma¬ 
nent partitions, and should be located accordingly. 

A heavy bulkhead is now constructed at the bottom of the 
shaft, and a chute arranged under the large compartment h, by 

which the loose ma¬ 
terial excavated above 
and thrown into this 
compartment may be 
drawn and loaded as 
required. To control 
the descent of the 
loose material in this 
compartment, a door 
is arranged at the foot 
of the chute. The 
compartment m serves 
the double purpose of 
a manway and air- 
shaft, and for this 
purpose it is divided 
by a temporary par¬ 
tition. A ladder is 
constructed in the 
manway, by which the workmen travel up and down. 

In the operation of upraising, the workmen ascend the man¬ 
way by the ladder and stand on a temporary platform, or 
on the loose material that is allowed to fill the compartment h. 
The material is drawn from this compartment only as is 
required to furnish good standing room at the face. 

8 G. In upraising, the ventilation of the shaft is always 
more or less difficult, owing to the tendency of the smoke and 










































DRIFTS, SLOPES, AND SHAFTS, PART 2 115 


hot bad air to remain at the top. The air compartment may 
be connected, by a box, to the main air-course while the man¬ 
way is open to the return, or vice versa; by this means, a fair 
current of air may be maintained at the top of the shaft or 
upraising. At times, a small blower is used to blow the air 
into the face. When compressed air is used to operate the 
drills, there will be air sufficient for the ventilation of the 
upraise without making other provision. The timbers required 
must be taken up the manway or the; air compartment. When 
blasting, the manway and air compartments are covered with 
heavy planks, to avoid the material loosened by the blast falling 
down the shaft and breaking the ladders or partitions. 


CONTRACTS FOR SHAFT SINKING 

87. Details of Contract. —A bore-hole record of the 
various strata to be passed through is usually available, and the 
sinking contractor therefore knows what he must expect and 
bids accordingly. His contract generally requires him to sink 
a certain distance, or to a certain coal or ore body, to properly 
timber the whole shaft, and to put heavy timber, horn sets, 
water rings, etc. where he is directed by the owner. The sinker 
is often required to give bond for faithful performance of work 
and only a certain percentage of the price agreed on is 
paid at the end of each month, the remaining part being with¬ 
held until satisfactory completion of the contract. In order to 
protect the company against the filing of liens for unpaid 
labor or material, the contractor is often required to present 
all bills for material used in the prosecution of the work to 
the company; and to furnish the company with a correct pay 
roll of all labor employed each month; such bills and pay rolls 
to be paid directly by the company and charged to the con¬ 
tractor’s account, and deducted from any amount due him on 
the contract. 

88 . The head-frame, engines, pumps, and explosives may 
be furnished by either party as may be agreed on. The owner 
or operator of the property usually furnishes the power and 
men for hoisting the material excavated and any water above 



116 DRIFTS, SLOPES, AND SHAFTS, PART 2 


a certain limited amount, the lumber, and other supplies, such 
as cement, nails, etc. The contractor usually furnishes the 
drills and other tools and the drillers and laborers. 

When inviting bids for a contract for sinking a shaft, the 
company is expected to provide a set of specifications giving 
such information as may be in their possession that will enable 
the bids for the work to be made intelligently, and stating 
the exact requirements that will afterwards form part of the 
contract. 

A date is set by the company when all the bids received will 
be opened, examined, and the contract awarded, often “to the 
lowest responsible bidder.” The company usually, however, 
reserves to itself the right to reject any or all bids. Where a 
bond is required, it is sometimes requested that the nature of 
the bond be submitted with the bid for the approval of the 
company. 

89. Specimen Form of Contract. — No form of con¬ 
tract can be given that will be of universal application, but the 
following form will serve as a guide in drawing up such 
contracts: 

This Agreement made this_day of_A. D. 19_, 

between_of_, in the County of 

_and State of_, party of the first part 

and_of_, in the County of_, 

State of_, party of the second part. 

Witnesseth, That the party of the first part, for and in consideration 
of the agreements hereinafter contained and for the further sum of one 
dollar ($1) to him in hand paid, the receipt whereof is hereby acknowl¬ 
edged, agrees to sink a shaft upon the property of party of the second 
part located in_, in accordance with the plans and specifi¬ 

cations furnished by the party of the second part and which form part 
of this agreement, and which shall remain the property of the party of 
the second part, and to turn over the completed work within the time 
hereinafter specified, free from all liens or encumbrances whatsoever, 
for the final inspection and acceptance of the party of the second part. 

The party of the second part agrees to furnish the party of the first 
part from time to time, as requested, such further plans or explana¬ 
tions as may be necessary to detail and illustrate the work to be done, 
and they shall form part of the contract, so far as they may be con¬ 
sistent with the original plans and specifications. 













DRIFTS, SLOPES, AND SHAFTS, PART 2 117 


Art. I. Dimensions. —The shaft is to be_ (_) feet 

long and- (_) feet wide in the clear, and in order to 

keep the shaft true to size and plumb, six lines must be suspended, one 
in each corner and one in the middle on each side, as directed by the 
party of the second part, and no points in the ends or sides of the 
completed shaft shall project outside these lines. The corners to be 
well squared, and all loose rock in the walls of shaft must be trimmed 
down and made secure as the work advances. 

Art. II. Depth. —The depth of shaft to be about_ 

(-) feet, or from the surface to a point_feet below the 

-vein or seam, the twelve feet below the_vein 

or seam being for a sump. 

Art. III. Water. —The party of the first part agrees to make all 
lodgments or sumps for water where and when required and rings for 
conducting the water to the sump, to make all platforms for setting of 
pumps and roofs for protecting the same from falling debris from 
blasts or otherwise, and to do all necessary work in the shaft for the 
protection of machinery and pipes placed therein, as directed from 
time to time by the party of the second part. 

Art. IV. Work. —The party of the first part agrees to prosecute 
the work with all possible vigor and despatch, and in a good work¬ 
manlike manner. As many men must be worked on a shift as the party 
of the second part thinks proper and three (3) shifts of eight (8) hours 
each must be worked in every 24 hours except Sunday. Steam or air 
drills will be allowed after the first 25 feet, except in rock where in the 
judgment of the party of the second part it will be detrimental to the 

shaft. If steam or air drills are used, at least_machines must 

be used at one time when required. 

Art. V.—Should the party of the first part at any time refuse or 
neglect to supply a sufficiency of properly skilled workmen, or of mate¬ 
rials of the proper quality, or fail in any respect to prosecute the work 
with promptness and diligence, or fail in the performance of any of 
the agreements herein contained, the party of the second part shall be 

at liberty, after_days’ written notice to the party of the first 

part, to provide any such labor or materials, and to deduct the cost 
thereof from any money then due or thereafter to become due to the 
party of the first part under this contract; or to terminate the contract 
and to enter upon the premises and take possession, for the purpose 
of completing the work comprehended under this contract, of all mate¬ 
rials, tools, and appliances thereon, and to employ any other person 
or persons to finish the work, and to provide the materials therefor; 
and in case of such discontinuance of the contract the party of the first 
part shall not be entitled to receive any further payment under this 
contract until the said work shall be wholly finished, at which time, if 
the unpaid balance of the amount to be paid under this contract shall 
exceed the expense incurred by the party of the second part in finish- 













118 DRIFTS, SLOPES, AND SHAFTS, PART 2 


ing the work, such excess shall be paid by the party of the second part 
to the party of the first part; but if such expense shall exceed such 
unpaid balance, the party of the first part shall pay the difference to 
the party of the second part. The expense incurred by the party of 
the second part as herein provided, either for furnishing materials or 
for finishing the work, and any damage incurred through such default, 
shall be audited and certified by a board of three arbitrators, each 
party selecting one and these two choosing a third, and the certified 
findings of such board of arbitrators shall be conclusive upon the 
parties. If the party of the first part or any of his employes conduct 
himself improperly or does anything to injure the work, he shall be 
discharged immediately. 

Art. VI. Labor and Material. —The party of the first part must 
furnish all necessary help and material for the execution of the work, 

except as hereinafter mentioned, and render not later than the_ 

day of each month the time and wage rate per day of each man and 
boy that has worked for him on said shaft during the previous month. 

And the said party of the first part hereby authorizes and directs the 
party of the second part as far as the party of the second part shall be 

indebted to the party of the first part, to pay on the_day of each 

month on a pay roll to be made out and approved by both the parties 
of the first and second parts, such sums as may be due as stated in said 
pay roll to the employes of the first party, and to charge the total of 
the amounts so paid to the account of first party, deducting such 
amount from any money due or that may become due later on the 
contract. 

Art. VII. Machinery. —The party of the second part agrees to 
furnish machinery and power and a hoisting engineer for hoisting from 

the shaft, and when the amount of water exceeds_ (_) 

buckets per hour, he will furnish pump and one machinist to assist the 
party of the first part to put the pump and pipes in place. He will 
also furnish iron and ties for track to dump and cars for same, and 
all lumber and nails required inside the shaft. 

Art. VIII. Timbering. —The work of timbering, putting in bun- 
tons, guides, and so forth, will be done by the party of the first part, 
and if not put in satisfactorily to the party of the second part, the 
party of the second part reserves the right of stopping the party of the 
first part and his men, and of putting them in himself with his own 
men, at the expense of the party of the first part. 

Art. IX. Payment. —The said party of the second part hereby 
agrees to pay to the said party of the first part in the manner and at 

the rates following, to wit: the sum of_dollars (_) 

per linear yard for each and every yard of surface or drift sunk, and 

-dollars (_) per linear yard for each and every linear 

yard of rock driven. Gravel and boulders do not constitute rock, in 
the meaning of this contract, except boulders of considerable size and 










DRIFTS, SLOPES, AND SHAFTS, PART 2 119 


frequency requiring continued blasting. An occasional boulder requir¬ 
ing to be blasted is not to be classed as rock. 

The party of the second part shall be given monthly estimates of the 
amount of work done by the party of the first part. 

And the said party of the second part further agrees that he will pay 

to the said party of the first part on or before the_ (_) 

day of each month for the work done during the preceding month at 
the prices hereinbefore agreed to be paid for said work, after deduct¬ 
ing therefrom the amount paid to the men employed by the said party 
of the first part at the times and in the manner hereinbefore specified, 
provided that in no case shall the said party of the second part be liable 
for services rendered by any person or persons employed by the said 
party of the first part to any greater extent or amount than there shall 
be due the said party of the first part for work done as heretofore 
agreed. 

And further, the said party of the second part shall have the right 
to retain from the monthly payments due first party and hereinbefore 
agreed to be made upon each monthly estimate, the sum of ten (10) 
per cent, of such estimate, for the first hundred feet or fraction thereof, 
seven and one-half (7i) per cent, for the second hundred feet or frac¬ 
tion thereof, five (5) per cent, for the third hundred feet or fraction 
thereof, and two and one-half (2J) per cent, for any fraction of the 
remaining distance until the completion of said shaft, satisfactorily to 
the party of the second part. The amount so retained to be paid to the 
said party of the first part upon the acceptance of the work by the 
second party when the shaft shall have been completed in accordance 
with the terms of this contract and to the perfect satisfaction of the 
party of the second part. 

Art. X. Acceptance of Work. —Upon the completion of the work 
and within the time hereinbefore specified, the party of the first part 
shall signify, in writing, his readiness to turn over the work for the 
final inspection and acceptance of the second party; such inspection and 
acceptance to be made by the duly qualified officers or agents of said 

second party, within_days after the receipt of the notice that 

the work is ready for them. 

The party of the first part shall not remove any of the machinery, 
tents, tools, or other implements used in the work from the ground, 
until after receiving the written acceptance of the work by the said 
second party, which machinery, tents, tools, and implements shall 
remain subject to attachment by said second party in case of a deficit 
in the final settlement. 

After the final inspection and before accepting the work, the party 
of the second part shall have the right to advertise for any unpaid 
claims for labor or material used in the work, a certain length of time 
as may be required by law*, before writing the final acceptance of the 
work, permitting the removal of the chattels belonging to the first 





120 DRIFTS, SLOPES, AND SHAFTS, PART 2 


party. In case the total amounts paid by the second party for labor 
and material and chargeable to the first party shall exceed the total 
amount to be paid for the work under the terms of this contract, the 
said second party shall have the right to attach and hold the aforesaid 
chattels, machinery, tents, tools, and other implements used during the 
prosecution of the work, to recoup the amount of such deficit. 

Art. XI. Responsibility.— The party of the first part will be 
responsible for all accidents on his own part, or on the part of any one 
of his men, and will save harmless the party of the second part from all 
claims for damage for injuries received by any of them in the prosecu¬ 
tion of the work. 

The party of the first part will provide for the ventilation of the 
shaft during sinking and will see that all the requirements of the Mine 
Law are strictly complied with. 

In witness whereof the parties of these presents have hereunto set 

their hands and seals this_day of_19_ 

_[seal]. 

_1_[seal]. 



































LIBRARY OF CONGRESS 






















































